Carpet Calculator — The Standard Says There Is No Standard for Pattern Repeat
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This selector governs every field, label, result and export here, and it overrides the site header switch. Roll widths are product designations, so the metric figure beside one is a conversion of what you entered rather than a product sold in that size.
The Base Quantity, From the Flooring Calculator
In feet, from the Flooring Calculator or a supplier quote. This page does not compute it and will not ask for a room size. A zero or a negative is treated as an entry error rather than a small job.
A whole number, from the same source. The roll width to strip count arithmetic belongs to the Flooring Calculator and is not repeated here.
A whole number, from the same source. Published guidance gives the seam count on a simple run as one less than the strip count, and this page takes the figure rather than deriving it because a real seam plan is not always that. Zero is an answer.
In feet, from the product. Published standard widths are 12 and 15 feet imperial and 4 and 5 metres metric. A 12 foot roll and a 4 metre roll are different products rather than conversions of each other.
In square feet, from the same source, and needed for the pad. It is entered rather than derived because the pad covers the floor while the carpet bought carries the pattern addition, the offcuts and the selvage.
The Pattern
A standard or full drop repeat matches side to side as well as up and down. A drop match is offset and is not identical from side to side. The published test is to cut a rectangle evenly across the width and drop the top half beside the lower: a standard pattern aligns and a drop match does not.
The Pile and the Seams
Nothing on this page can detect it and everything on the job depends on it. All strips in a room must have pile running the same way, and mixing directions creates a visible colour-shading line at every seam and around any remnant rotated 180 degrees.
The brightest source, normally a window. The seam rule locates seams away from it, because light skimming across a seam at a shallow angle is what makes it visible.
The way people walk through the room. The seam rule locates seams perpendicular to it. Both this and the light source are needed before any placement is reported.
For the selvage qualifier. Published guidance states that some woven carpet selvages must not be trimmed and that the manufacturer's recommendation governs, so the one inch per side figure is not universal.
In feet, for the seam tape. Tape and sealer are consumed by the seam rather than by the area, so this needs the length of the seams rather than the size of the room.
The Pad, the Gripper and the Gully
In inches, for the two gully figures. At the wall the gully is slightly less than the thickness and not exceeding 3/8 inch, and between strips on a stair it is slightly less than double the thickness, so the two move in opposite directions as the carpet thickens.
In square feet per roll, from the product. Published figures give pad rolls at 6 feet by 45 feet, which is 270 square feet, and a pad roll width is not the carpet roll width. The roll count runs on the floor area rather than on the carpet bought.
In feet, for the tackless gripper strip. Doorways are subtracted below, because a doorway carries a transition rather than a gripper.
In feet, the total width of the doorways in that perimeter. It comes off the gripper length and is where the transitions sit.
A whole number. This count is what drives Z-bar against binder bar, because a carpet to carpet transition takes the first and a carpet to hard surface one takes the second.
A whole number, for the binder bar count. These sit in the same doorways taken off the gripper length above.
The Stairs
A whole number. No per-step carpet quantity is issued from it, because no published source gives one. The block names the method and reports the published stair detailing instead.
The two methods published by name. The method changes the detailing rather than producing a quantity here: on a waterfall, tack strip goes on the risers as well with pins pointing down to the tread, and with a cap-and-band or contoured technique tack strip is not used on the riser.
Prices, Optional
In your own currency, per square yard. The cost runs on the order square yards, which on a repeat pattern carries the pattern addition and on a carpet with no repeat is the same figure as the base.
In your own currency, per roll, on the roll count above.
In your own currency, per 4 foot piece, on the piece count above.
In your own currency, per seam, on the seam count you entered.
In your own currency, per stair, on the stair count you entered. It is arithmetic on a count and a price and carries no carpet quantity, because none is published.
Overview
This page starts from linear feet, strips and seams. If you need carpet from a room size and a roll width, the Flooring Calculator does that first and this one takes its answer.
What it does instead is the part that page leaves alone, and the biggest piece of it has no settled rule.
Published CRI 105, the residential carpet installation standard, states in its own words that there are no industry standards for carpet pattern variations.
So the two methods in circulation are both trade practice. One says patterned goods add one repeat of length per seam. The other says strip cut lengths can only exist in whole multiples of the repeat, so every cut rounds up to the next one.
They give different answers and neither is consistently larger. On a 5.10 metre run at a 0.91 metre repeat the first gives 6.01 metres and the second gives 5.46. At a 0.50 metre repeat the flat method always adds 0.50 while the quantised method adds nothing at all on a 5.00 metre run.
And the repeat itself is not fixed. The standard tells the fitter to sequence cuts from the longest measured repeat down to the shortest within the dye lot, which is an instruction that only exists because it varies inside one lot.
What to Look at First
Start with the pattern, because it decides what the rest of the page can tell you. A solid or random texture takes no pattern addition, so the square yards before the pattern and the square yards to order come out as the same figure. A standard or full drop repeat and a drop match both take one, and then the order figure is the one a price per square yard applies to.
On a repeat pattern the page then asks which method that addition follows. There is no industry standard for it, so nothing here is a default: the two length rules in circulation and a supplier's stated percentage are all offered, and Not sure is an answer that reports them together and issues no order figure until you pick one.
How to Use This Calculator
Get the linear feet, the strips and the seams from the Flooring Calculator or a supplier quote. This page does not compute them and will not ask for a room size.
If the carpet has a repeat, choose which pattern method you want, or say you are not sure. The standard sets none, the two length rules in circulation give different answers, and a supplier's stated percentage is offered as a method of its own, so the page reports the ones you did not pick beside the one you did. Not sure is an answer: the page shows them together, selects no order quantity, and tells you what to ask the supplier.
Read the two square yard figures. The one before the pattern is what you came in with. On a repeat pattern the one to order carries the addition the method you chose produced and is the figure a price per square yard applies to; on a solid or random texture there is no addition, so the two are the same figure; and while the method is left at Not sure, no order figure is issued at all.
Answer the pile direction. Nothing on this page can detect it and a remnant laid the wrong way round is a shading line rather than a fit.
Give the light source and the traffic direction if you know them. The seam rule needs both, and the reason it works is that light skimming across a seam is what makes it visible.
Treat the stair block as a method rather than a quantity. The standard describes the two methods in detail and gives no figure per step, so neither does this page.
Inputs & Outputs
Inputs
Outputs
Carpet Formula
Every figure here starts from linear feet that were computed somewhere else. Which equations run depends on the pattern and on which of the two trade methods you choose.
The Pattern Addition, One Repeat Per Seam
add_flat_ft = seams * repeat_ft
total_flat_ft = lin_ft + add_flat_ft
This method always adds exactly one repeat per seam, whatever the run.
The Pattern Addition, Quantised To Whole Repeats
reps_per_strip = run_ft / repeat_ft
strip_q_ft = reps_rounded * repeat_ft
total_quant_ft = strip_q_ft * strips
add_quant_ft = total_quant_ft - lin_ft
The repeats in one strip figure is rounded up before the strip length equation uses it, and the rounded value is named separately in that equation so the rounding is visible rather than implied. Rounding is a function rather than an arithmetic expression and is stated here: a strip cut length can only exist in a whole number of repeats.
Every strip cut length rounds, including the first. A cut that is not a whole number of repeats cannot be matched to the one beside it, and the first strip has a neighbour like every other.
The Two Methods Compared
method_gap_ft = total_flat_ft - total_quant_ft
Both methods run on every repeat pattern and the one you did not choose is reported beside the one you did. No figure between them is issued, because they are two models of what a pattern does to a strip rather than two estimates of one quantity.
The Pattern Addition As A Percentage
add_pct_ft = lin_ft * pat_pct / 100
total_pct_ft = lin_ft + add_pct_ft
A third figure circulates as a percentage, at 10 to 20 percent for large-repeat patterned carpet from a manufacturer install guide. It is neither of the length methods and the page offers it as its own answer rather than folding it in.
The Two Square Yard Figures
sq_yd_base = lin_ft * roll_w_ft / 9
sq_yd_order = total_method_ft * roll_w_ft / 9
There are two square yard figures and the order runs on the second. The base figure is the entered linear feet at the roll width, which is what the Flooring Calculator produced. The order figure is the pattern adjusted total at the same roll width, and a price per square yard applies to it. Reporting only the base would put the pattern addition in one row and the money on a different quantity in another.
The total method figure is whichever total the chosen method produced: the flat total, the quantised total, the percentage total, or the entered linear feet where the carpet is solid or random texture. Where no method has been chosen, no order figure is issued at all.
The square yards equations multiply linear feet by the roll width, because carpet is quoted by the square yard and sold by the linear foot off a roll of fixed width.
The Selvage Trim
selvage_width_ft = seams * 2 / 12
The equation takes about one inch from each of the two strips that meet at a seam, and its answer is a WIDTH rather than a length. Every other figure in feet on this page is linear feet of carpet off a roll. This one is inches trimmed off the sides of strips, and adding it to the linear feet would be adding a width to a length.
Published guidance states that some woven carpet selvages must not be trimmed and that the manufacturer's recommendation governs, so the figure carries that qualifier rather than being universal.
The trim can matter to a strip plan this page did not make. The strip count came from the Flooring Calculator, which worked from the roll width without the seam trim, so a plan that only just fits can stop fitting once two inches come off each seamed edge. The page reports the trim and does not redesign the layout.
The Pad, The Gripper And The Seam Tape
pad_rolls = floor_sf / pad_roll_sf
tack_ft = perimeter_ft - doorway_ft
tack_pieces = tack_ft / piece_ft
tape_ft = seams * seam_len_ft
The pad rolls equation runs on the floor area rather than on the carpet bought, because a pad covers the floor and the carpet bought carries the pattern addition, the offcuts and the selvage. Both figures are entered from the Flooring Calculator and neither is derived here.
The piece length is the published 4 foot tackless gripper strip. All pad roll, strip piece and transition counts round up once, at the end.
The Two Gully Figures
gully_thick_in = carpet_t_in
gully_cap_in = 0.375
gully_stair_in = carpet_t_in * 2
The gully figures are maximums rather than targets, and the wall one has two of them. Published guidance gives the wall gully as always slightly less than the carpet thickness AND not exceeding 3/8 inch, so the governing figure is the lower of the two and the page reports both with the one that governs named. On a 1/4 inch carpet the thickness governs at 0.25. On a 1/2 inch carpet the cap governs at 0.375. Taking the lower of two figures is a function rather than an arithmetic expression, which is why the two are separate equations here and the comparison is stated in prose.
The stair gully is a different rule on the same measurement, at slightly less than double the carpet thickness, and it is never substituted for the wall figure. One is bounded above by 3/8 inch and the other is twice the thickness, so the two move in opposite directions as the carpet gets thicker.
Unit Conversions
sq m = sq yd * 0.836127
m = ft * 0.3048
mm = in * 25.4
No equation here derives the linear feet, the strips or the seams from a room. Those are entered.
The Standard Says There Is No Standard for Pattern Repeat
Every carpet page that mentions pattern repeat gives one rule. There are two in circulation, they are not variations of each other, and the standard everybody cites sets neither.
Published CRI 105, the standard for installation of residential carpet, states that there are no industry standards for carpet pattern variations.
That sentence settles the question by refusing it. Neither method comes from the standard. Both are trade practice.
The first is flat: patterned goods add one repeat of length per seam. It is attributed to the installation standard and a manufacturer pattern-match guide by a calculator site, and it always adds exactly one repeat per seam whatever the run.
The second is quantised: strip cut lengths can only exist in multiples of the repeat, so every cut rounds up to the next whole repeat. Published guidance adds that the larger the repeat, the coarser that rounding becomes.
They give different answers and neither is consistently larger.
On a 5.10 metre run the flat method gives 5.40, 5.60 and 6.01 metres at repeats of 0.30, 0.50 and 0.91. The quantised method gives 5.10, 5.50 and 5.46.
The quantised method adds nothing at all where the run is already a whole number of repeats. On a 5.00 metre run at a 0.50 metre repeat it adds zero and the flat method adds 0.50. On a 5.10 metre run at the same repeat it adds 0.40 and the flat method still adds 0.50.
So a reader who takes one figure from one source and one from another is not looking at a disagreement about how much to add. They are looking at two different models of what the pattern does to a strip.
This page asks which one, computes it, and reports the other beside it with the gap named. It issues no figure between them, because a midpoint of two models describes nothing.
A third figure circulates as a percentage: 10 to 20 percent for large-repeat patterned carpet, from a manufacturer install guide. It is neither of the length methods and the page offers it as its own answer rather than folding it in.
One wording of the quantised method says every strip after the first rounds up, which would leave the first strip at its measured length. This page rounds every strip, because a cut that is not a whole number of repeats cannot be matched to the cut beside it and the first strip has a neighbour too. On four strips of 5.10 metres at a 0.50 metre repeat the two readings give 22.00 and 21.60 metres, and the difference is exactly the rounding on strip one.
The Repeat on the Label Is Nominal
CRI 105 contains an instruction that only makes sense one way.
In the absence of sequencing information from the carpet manufacturer, it says, sequence carpet cuts working from the longest measured repeat gradually down to the shortest repeat within the dye lot.
Longest measured. Shortest. Within the dye lot.
That instruction exists because the repeat is not the same on every cut from one roll of one dye lot. If it were, there would be nothing to sequence.
So the figure printed on the sample or the label is nominal, the fitter measures the actual repeat on each cut, and the order the cuts go down in is chosen to spread the drift rather than concentrate it at one seam.
The same standard adds two statements in the same register: patterned carpet requires additional material for proper pattern matching, and pattern adjustment during installation should be anticipated. It also requires that the seaming diagram reflect the desired pattern direction, and notes that alignment of patterned carpet typically requires mechanical stretching devices.
None of that is arithmetic and all of it changes what a number on this page means. So the page reports the pattern addition from the nominal repeat, and states that the repeat is nominal, that the standard has the fitter measuring, and that adjustment is expected rather than exceptional.
Pile Direction Is Not Aesthetics
Published guidance is direct: all strips in a room must have pile running the same way, and mixing directions creates a visible colour-shading line at every seam and around any remnant rotated 180 degrees.
The roll carries a with-pile arrow on the back for exactly this reason, and every strip goes down with the arrows pointing the same way.
That has a consequence for quantity that a square yard figure cannot express. A remnant that fits an opening perfectly, laid the other way round, is not a fit. It is a piece of carpet the same size and a different colour under the same light, and it will read as a patch for the life of the floor.
Pile is also why traffic shading appears at all: foot traffic crushes pile in the walking direction, so the room develops a lighter path along the way people walk. That is not wear and it is not a fault.
This page asks whether the pile direction has been confirmed, reports the answer, and states what mixing it costs, because nothing in a linear foot figure carries that and the reader will not find out until the light is right.
On stairs the direction is prescribed rather than chosen. Most manufacturers recommend the pile direction run down the stairs, and pins on the tread point toward the riser.
The Seam Rule Has a Mechanism
Published guidance attributed to section 7 of the installation standard gives the rule: locate seams perpendicular to the main traffic direction and away from the brightest light source.
Most pages stop there, and a rule without a reason cannot be applied to a room the writer has not seen.
The reason is given: light skimming across a seam is what makes it visible. Not light on the seam, light across it at a shallow angle.
That turns the rule into something a reader can use. The brightest light source in most rooms is a window, the skimming angle is low in the morning and the evening, and the seam to worry about is the one running towards the window rather than across it.
Two more instructions sit in the same place. The factory selvage is trimmed from each strip, about an inch per side, so every seam consumes two inches of width. And the pattern is matched at the midpoint of the seam's length, working out from the midpoint in both directions rather than from one end.
The selvage figure carries a qualifier that most pages drop. Some woven carpet selvages must not be trimmed, and the manufacturer's recommendation governs.
The trim is also a width rather than a length, which is why it is never added to the linear feet on this page. It matters to a strip plan instead: the strip count came from the Flooring Calculator, which worked from the roll width before the seam trim, so a plan that only just fits can stop fitting once two inches come off each seamed edge.
The Gully Is Two Rules With Opposite Multipliers
The gully is the space between the tack strip and the wall that the carpet edge is tucked into.
Published standard text gives it at the wall as always slightly less than the thickness of the carpet and not exceeding 3/8 inch. That is two limits on one measurement, and the governing figure is the lower of them. On a 1/4 inch carpet the thickness governs. On a 1/2 inch carpet the 3/8 inch cap governs.
The same standard gives a different rule for the gully between strips on a stair: slightly less than double the carpet thickness.
One rule is bounded above by 3/8 inch and the other is twice the thickness, so the two move in opposite directions as the carpet gets thicker. They are reported separately here and neither is ever substituted for the other.
This Page Does Not Compute the Linear Feet
The Flooring Calculator on this site takes a room and a roll width and returns the strips, the orientation comparison, the linear feet and the square yards. It carries the finding that roll goods waste is an orientation rather than a percentage, and it names four things it does not do: pattern repeat matching, pad and cushion, stairs, and the choice between orientations on anything except material.
This page is those four.
It takes the linear feet, the strips and the seams as inputs and computes none of them. A reader arrives with a number from that page or from a supplier quote and leaves with what happens to it.
The split is not tidiness. Two pages in one category that both derive a strip count from a room width will disagree the first time either rounding rule moves, and the reader who finds the difference has no way to tell which page is current. One page owns the room and the roll. This page owns the pattern, the pile, the seam and everything hanging off them.
What Is a Carpet Calculation
There are two carpet calculations and this page is the second one.
The first turns a room and a roll width into strips and linear feet. It is a geometry problem: a roll has a fixed width, a room rarely matches it, and which way the roll runs decides how much of the last strip is offcut. The Flooring Calculator does that.
The second is what happens to that number once the carpet has a pattern, a pile and a seam.
A pattern adds length, and how much depends on which of two unstandardised trade methods you follow. The repeat that drives it is nominal rather than exact, and the standard tells the fitter to measure each cut and sequence them. The pile has a direction that no arithmetic can see and that decides whether a remnant is a fit or a patch. The seam has a placement rule with a reason, and a selvage trim that is not universal.
None of it is difficult arithmetic. All of it changes the order, and the parts that change it most are the parts with no settled figure behind them.
Key Facts
- Published CRI 105, the standard for installation of residential carpet, states that there are no industry standards for carpet pattern variations.
- Two methods for the pattern addition circulate as trade practice. The flat method adds one repeat of length per seam. The quantised method rounds every strip cut length up to the next whole repeat.
- They give different answers and neither is consistently larger. On a 5.10 metre run the flat method gives 5.40, 5.60 and 6.01 metres at repeats of 0.30, 0.50 and 0.91, and the quantised method gives 5.10, 5.50 and 5.46.
- At a 0.50 metre repeat the flat method always adds 0.50, while the quantised method adds nothing on a 5.00 metre run, 0.40 on 5.10 and 0.01 on 5.49.
- A third figure circulates as a percentage, at 10 to 20 percent for large-repeat patterned carpet from a manufacturer install guide, and it is neither of the length methods.
- The standard instructs that in the absence of sequencing information from the manufacturer, carpet cuts are sequenced working from the longest measured repeat gradually down to the shortest repeat within the dye lot.
- That instruction exists because the repeat varies within one dye lot, so the figure on the label is nominal and the fitter measures each cut.
- The standard states that patterned carpet requires additional material for proper pattern matching, and that pattern adjustment during installation should be anticipated.
- It requires that the seaming diagram reflect the desired pattern direction, and notes that alignment of patterned carpet typically requires mechanical stretching devices.
- A standard or full drop repeat matches side to side as well as up and down. A drop match is offset, is harder to seam and needs more material, and no published figure gives how much more.
- All strips in a room must have pile running the same way, and mixing directions creates a visible colour-shading line at every seam and around any remnant rotated 180 degrees.
- The roll carries a with-pile arrow on the back, and pile is why traffic shading appears, because foot traffic crushes pile in the walking direction.
- Seams are located perpendicular to the main traffic direction and away from the brightest light source, because light skimming across a seam is what makes it visible.
- The pattern is matched at the midpoint of the seam's length, working out from the midpoint.
- The factory selvage is trimmed from each strip, about one inch per side, but some woven carpet selvages must not be trimmed and the manufacturer's recommendation governs.
- The gully at the wall should always be slightly less than the thickness of the carpet and not exceeding 3/8 inch, so on carpet thicker than 3/8 the cap governs rather than the thickness.
- The gully between strips on a stair is required to be slightly less than double the carpet thickness.
- Most manufacturers recommend the carpet pile direction run down the stairs, and pins on the tread point toward the riser.
- On a waterfall stair installation tack strip goes on the risers as well, with pins pointing down to the tread, and with a cap-and-band or contoured technique tack strip is not used on the riser.
- For a turned finish on stairs, tack strip and cushion are about 1.5 inches, 38 mm less than the carpet width.
- The standard gives installation conditions as an indoor temperature between 65 and 95 degrees Fahrenheit, 18 to 35 Celsius, with humidity between 10 and 65 percent, maintained for at least 48 hours before and during and 72 after.
- Published pad rolls are 6 feet by 45 feet, which is 270 square feet, and tackless gripper strip comes in 4 foot pieces.
Applications
- Someone with linear feet from the Flooring Calculator finds out what a pattern does to them.
- A reader quoted two different figures by two suppliers sees both trade methods and which one each came from.
- Someone with a large repeat learns that the quantised method can add nothing or almost a whole repeat depending on the run.
- A reader planning to reuse a remnant finds out that turning it round makes it a patch.
- Someone with a window at one end of a room gets the seam rule with the reason that makes it applicable.
- A reader ordering pad finds that it runs on the floor area rather than on the carpet bought.
- Someone carpeting stairs gets the method described in detail and no invented per-step figure.
- A reader pricing the job finds which of the two square yard figures the money runs on.
Example Calculations
Example 1. Two methods, one run, and they cross over
Given: a 5.10 metre strip run with a 0.91 metre pattern repeat.
Flat method: one repeat of length per seam, so the addition is 0.91 metres and the strip becomes 6.01.
Quantised method: 5.10 divided by 0.91 is 5.60 repeats, which rounds up to 6, and 6 repeats is 5.46 metres.
Result: 6.01 against 5.46, a gap of 0.55 metres on one strip.
Now change the repeat to 0.50 and the run to 5.00. The flat method still adds 0.50 and gives 5.50. The quantised method finds 5.00 is exactly 10 repeats, rounds nothing, and gives 5.00.
The flat method always adds one repeat. The quantised method adds between nothing and one repeat. Neither is consistently larger, and CRI 105 sets neither, because it states that there are no industry standards for carpet pattern variations.
Example 2. Four strips, and which ones round
Given: four strips of 5.10 metres at a 0.50 metre repeat, on the quantised method.
Each strip rounds up to 5.50 metres, the first included.
Four strips at 5.50 is 22.00 metres.
Result: 22.00 metres. One published wording says every strip after the first rounds, which would give 5.10 plus three at 5.50, or 21.60.
The difference is 0.40 metres, which is exactly the rounding on strip one. This page rounds every strip, because a cut that is not a whole number of repeats cannot be matched to the cut beside it and the first strip has a neighbour like every other.
Example 3. The two square yard figures, and which one you pay for
Given: 100 linear feet of a 12 foot roll, three seams, a 0.91 metre repeat on the flat method.
Base: 100 times 12 divided by 9 is 133.33 square yards. That is the figure the Flooring Calculator produced.
The flat method adds three repeats, which is 2.986 feet each, or 8.96 feet, so the total is 108.96 linear feet.
Order: 108.96 times 12 divided by 9 is 145.28 square yards.
Result: 133.33 and 145.28, and a price per square yard applies to the second. Reporting only the base would put the pattern addition in one row and the money on a different quantity in another, which is 11.95 square yards of carpet nobody priced.
Example 4. The repeat you measure is not the repeat on the label
Given: patterned carpet from one dye lot.
The standard instructs that in the absence of sequencing information from the manufacturer, carpet cuts are sequenced working from the longest measured repeat gradually down to the shortest repeat within the dye lot.
Result: that instruction only makes sense if the repeat differs between cuts from one lot. If it were constant there would be nothing to sequence.
So the figure on the label is nominal, the fitter measures each cut, and the order the cuts go down in is chosen to spread the drift rather than concentrate it at one seam. The standard adds that pattern adjustment during installation should be anticipated, and that alignment typically requires mechanical stretching devices.
None of that is arithmetic, and all of it is what the number on this page is an estimate of.
Example 5. The remnant that fits and is not a fit
Given: a 4 by 6 foot offcut and a 4 by 6 foot alcove.
The area matches exactly. The arithmetic says it fits.
Result: it fits only if the pile runs the same way as the rest of the room.
Published guidance states that all strips must have pile running the same way and that a remnant rotated 180 degrees creates a visible colour-shading line. The roll carries a with-pile arrow on the back for this reason.
So a piece of the same carpet, the same size, laid the other way round, is a different colour under the same light, and it will read as a patch for the life of the floor. No square foot figure on any page can see that, which is why this one asks whether the pile direction has been confirmed rather than assuming it has.
Example 6. The two gully figures on one carpet
Given: a 1/2 inch carpet at the wall and on a stair.
At the wall the rule is slightly less than the thickness AND not exceeding 3/8 inch, so the cap governs at 0.375 inch rather than the thickness at 0.5.
Between strips on a stair the rule is slightly less than double the thickness, which is 1 inch.
Result: 0.375 inch at the wall and 1 inch on the stair, from one carpet thickness. On a 1/4 inch carpet the wall figure moves to 0.25, because the thickness is then the lower of the two, while the stair figure moves to 0.5. The two limits move in opposite directions as the carpet thickens, so neither is ever used in place of the other.
Standards & References
- The Carpet and Rug Institute The trade association publishing the installation standards cited on this page.
- CRI 105 Standard for Installation of Residential Carpet The standard giving the pattern sequencing instruction, the statement that there are no industry standards for carpet pattern variations, the seam and selvage provisions, the gully figures and the stair methods.
- CRI 104 Standard for Installation of Commercial Carpet The commercial companion standard.
- Carpet Cushion Council The body behind the cushion classes and the HUD UM 72a cushion specification referenced in carpet estimating.
- ASTM D5252 Standard Practice for the Operation of the Hexapod Tumble Drum Tester One of the durability tests referenced for carpet performance.
- ASTM D5417 Standard Practice for Operation of the Vettermann Drum Tester The companion durability test.
- NIST Special Publication 811, Guide for the Use of the International System of Units The authority for the conversion factors used on this page.
The pattern statements, the sequencing instruction, the gully figures, the selvage qualifier, the stair provisions and the installation conditions are quoted from CRI 105 rather than paraphrased, and the standard's statement that there are no industry standards for carpet pattern variations is the reason this page reports two trade methods rather than one.
Neither the flat method nor the quantised method comes from the standard. The first is attributed to the standard and a manufacturer guide by a calculator site, the second appears on a separate calculator site, and the percentage figure of 10 to 20 percent comes from a manufacturer install guide. This page asks which the reader wants and reports the other beside it, and it issues no figure between them, because they are two models of what a pattern does to a strip rather than two estimates of one quantity.
The section numbers a calculator site attributes to the standard for the seam placement rule have not been read against the standard text and are named as attributed rather than as read. No per-step stair quantity appears in any source consulted and none is issued.
The linear feet, the strips, the seams and the floor area are entered rather than computed. The room to linear feet arithmetic, the roll width to strip arithmetic and the orientation comparison are the Flooring Calculator's, and computing them again here would put two pages in this set in disagreement the first time either changed. This page reports quantities and issues no pass or fail.
Units
Carpet is quoted by the square yard, which is 9 square feet and 0.836127 square metres. 133.33 square yards is 111.48 square metres.
Linear feet and roll widths are in feet with metres alongside at 0.3048. A 12 foot roll is 3.658 metres and 100 linear feet is 30.48.
Pattern repeats, carpet thickness, gully figures and selvage trim are in inches with millimetres alongside at 25.4. A 0.91 metre repeat is 2.986 feet and 35.83 inches, a 3/8 inch gully is 9.53 mm, and the 1.5 inch stair allowance is the 38 mm the standard prints itself.
Roll widths are product designations rather than measurements. A 12 foot roll and a 4 metre roll are different products sold in different markets, not conversions of each other.
Pattern repeats are published in whichever unit the manufacturer uses, and a repeat entered in one unit is converted rather than reinterpreted.
Installation temperature is in degrees Fahrenheit with Celsius alongside: the published 65 to 95 degrees is the 18 to 35 Celsius the standard prints itself.
The strip count, the seam count, the pad roll count, the piece count and the pattern percentage are dimensionless or identical in both systems.
The internal unit selector governs the fields, labels, math, on-screen result and any exported result, and it takes priority over any site-wide unit switch. Switching converts the values you entered rather than reinterpreting them.
Limitations
- This page reports quantities and issues no pass or fail. The standard governs workmanship rather than quantity and sets no pattern figure at all.
- It does not compute the linear feet, the strips, the seams or the orientation from a room. Those come from the Flooring Calculator or a supplier quote.
- It issues no per-step stair quantity. The standard describes the waterfall and cap-and-band methods in detail and gives no figure per step, and no other source consulted gives one.
- It gives no figure for the extra material a drop match needs. Published guidance says it needs more and does not say how much.
- It does not choose between the two pattern methods. The standard sets none and the two in circulation are trade practice, so the page asks and reports both.
- It does not redesign a strip plan. The strip count came from the Flooring Calculator, which worked from the roll width before the seam trim, and this page reports the selvage trim without changing the layout.
- It does not draw a seam diagram. The standard requires the seaming diagram to reflect the desired pattern direction, and drawing one is a layout task rather than an arithmetic one.
- The selvage trim of about one inch per side is not universal. Some woven carpet selvages must not be trimmed and the manufacturer's recommendation governs.
- It does not select a carpet grade, fibre or construction, and it does not assess a subfloor or estimate installation labour.
- The section numbers attributed to the standard for the seam placement rule have not been read against the standard text.
- Any cost is arithmetic on a price you entered.
Common Mistakes to Avoid
- Expecting this page to take a room size. It starts from linear feet, and the Flooring Calculator is where a room becomes linear feet.
- Treating one pattern method as the rule. The standard states that there are no industry standards for carpet pattern variations, and the two in circulation give different answers.
- Assuming the quantised method always adds more than the flat one. It adds nothing at all where the run is already a whole number of repeats.
- Leaving the first strip unrounded on the quantised method. A cut that is not a whole number of repeats cannot be matched to the cut beside it, and the first strip has a neighbour like every other.
- Pricing the base square yards on a patterned carpet. The pattern addition belongs in the figure the money runs on, and the two differ by 11.95 square yards on 100 linear feet of a 12 foot roll at three seams.
- Taking the repeat on the label as exact. The standard has the fitter measuring each cut and sequencing from the longest measured repeat down to the shortest within the dye lot.
- Turning a remnant round to make it fit. It becomes a visible colour-shading line rather than a fit, and the roll carries a with-pile arrow to prevent exactly this.
- Running seams towards the window. Light skimming across a seam is what makes it visible, so seams go away from the brightest source and perpendicular to the main traffic direction.
- Matching the pattern from one end of a seam. The standard has it matched at the midpoint and worked out from there.
- Trimming the selvage on a woven carpet without checking. Some woven selvages must not be trimmed.
- Adding the selvage trim to the linear feet. It is a width off the sides of strips, not a length off the roll.
- Using the wall gully figure on a stair. At the wall the governing figure is the lower of the carpet thickness and 3/8 inch, and between strips on a stair it is less than double the thickness, so the two move opposite ways as the carpet thickens.
- Sizing the pad from the carpet bought. The pad covers the floor and the carpet bought carries the pattern addition, the offcuts and the selvage.
- Installing outside the published conditions. The standard gives 65 to 95 degrees Fahrenheit and 10 to 65 percent humidity, held 48 hours before and during and 72 after.
Frequently Asked Questions
How much extra carpet do I need for a pattern?
Which pattern method should I use?
Why does this calculator not ask for my room size?
Is the pattern repeat on the label exact?
Can I use a leftover piece the other way round?
Where should the seam go?
How much carpet does a stair take?
Which square yard figure do I pay for?
Frequently Used Together
Engineers often use these calculators in combination for complete project workflows:
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Explore similar calculators that might be useful for your project:
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This selector governs every field, label, result and export here, and it overrides the site header switch. Roll widths are product designations, so the metric figure beside one is a conversion of what you entered rather than a product sold in that size.
The Base Quantity, From the Flooring Calculator
In feet, from the Flooring Calculator or a supplier quote. This page does not compute it and will not ask for a room size. A zero or a negative is treated as an entry error rather than a small job.
A whole number, from the same source. The roll width to strip count arithmetic belongs to the Flooring Calculator and is not repeated here.
A whole number, from the same source. Published guidance gives the seam count on a simple run as one less than the strip count, and this page takes the figure rather than deriving it because a real seam plan is not always that. Zero is an answer.
In feet, from the product. Published standard widths are 12 and 15 feet imperial and 4 and 5 metres metric. A 12 foot roll and a 4 metre roll are different products rather than conversions of each other.
In square feet, from the same source, and needed for the pad. It is entered rather than derived because the pad covers the floor while the carpet bought carries the pattern addition, the offcuts and the selvage.
The Pattern
A standard or full drop repeat matches side to side as well as up and down. A drop match is offset and is not identical from side to side. The published test is to cut a rectangle evenly across the width and drop the top half beside the lower: a standard pattern aligns and a drop match does not.
The Pile and the Seams
Nothing on this page can detect it and everything on the job depends on it. All strips in a room must have pile running the same way, and mixing directions creates a visible colour-shading line at every seam and around any remnant rotated 180 degrees.
The brightest source, normally a window. The seam rule locates seams away from it, because light skimming across a seam at a shallow angle is what makes it visible.
The way people walk through the room. The seam rule locates seams perpendicular to it. Both this and the light source are needed before any placement is reported.
For the selvage qualifier. Published guidance states that some woven carpet selvages must not be trimmed and that the manufacturer's recommendation governs, so the one inch per side figure is not universal.
In feet, for the seam tape. Tape and sealer are consumed by the seam rather than by the area, so this needs the length of the seams rather than the size of the room.
The Pad, the Gripper and the Gully
In inches, for the two gully figures. At the wall the gully is slightly less than the thickness and not exceeding 3/8 inch, and between strips on a stair it is slightly less than double the thickness, so the two move in opposite directions as the carpet thickens.
In square feet per roll, from the product. Published figures give pad rolls at 6 feet by 45 feet, which is 270 square feet, and a pad roll width is not the carpet roll width. The roll count runs on the floor area rather than on the carpet bought.
In feet, for the tackless gripper strip. Doorways are subtracted below, because a doorway carries a transition rather than a gripper.
In feet, the total width of the doorways in that perimeter. It comes off the gripper length and is where the transitions sit.
A whole number. This count is what drives Z-bar against binder bar, because a carpet to carpet transition takes the first and a carpet to hard surface one takes the second.
A whole number, for the binder bar count. These sit in the same doorways taken off the gripper length above.
The Stairs
A whole number. No per-step carpet quantity is issued from it, because no published source gives one. The block names the method and reports the published stair detailing instead.
The two methods published by name. The method changes the detailing rather than producing a quantity here: on a waterfall, tack strip goes on the risers as well with pins pointing down to the tread, and with a cap-and-band or contoured technique tack strip is not used on the riser.
Prices, Optional
In your own currency, per square yard. The cost runs on the order square yards, which on a repeat pattern carries the pattern addition and on a carpet with no repeat is the same figure as the base.
In your own currency, per roll, on the roll count above.
In your own currency, per 4 foot piece, on the piece count above.
In your own currency, per seam, on the seam count you entered.
In your own currency, per stair, on the stair count you entered. It is arithmetic on a count and a price and carries no carpet quantity, because none is published.