EstimatorKitFree carpet calculator
Carpet cut from a 12 ft roll, seams and all
Enter a room and the roll it is coming off, and this returns the running feet to buy, the square yards that bills as, how many seams the layout needs and how much of the roll goes in the van unused. Carpet is not sold by the area of your floor: it comes off a roll 12, 13 ft 2 in or 15 ft wide, you pay for the full width of every foot you take, and how the room cuts out of that width decides the price far more than its square footage does.
- 100% free
- No signup
- 3 roll widths
- Both cut directions
- Sq yd and sq ft
Measure into the doorway and to the deepest point of any bay — carpet is cut to the biggest rectangle the room fits in, not to its outline.
The default for US residential broadloom.
Add the price you were quoted, in either unit
Stores quote both and the two differ by a factor of nine. Whichever you type, the other one is shown next to it.
Off a 12 ft roll, cuts running the width of the room
28 running ft
- Square yards billed
- 37.3
- Square feet billed
- 336
- Floor actually covered
- 243 sq ft
- Seams
- 1
- Cushion
- 27 sq yd
Which way to cut it
- Cuts running the width of the room: 2 cuts of 14 ft
- 336 sq ft
- Cuts running the length of the room: 2 cuts of 18.5 ft
- 444 sq ft
Cutting the width of the room buys 108 sq ft less. That is the cheaper plan, but it is not automatically the right one — a seam should run with the light from the main window and out of the walking line, so a fitter will sometimes take the dearer cut deliberately.
The offcut
You are paying for 336 sq ft and putting 243 sq ft on the floor, so 93 sq ft — 38.27% — goes in the van. Most of it is the strip left over from the 6' filler: a filler is cut from a full width of roll and the rest of that width cannot be turned sideways to use elsewhere, because the pile would run the wrong way and read as a different color.
It is also why this page reports an offcut rather than a percentage. The site keeps a waste figure for carpet and attaches a warning to it: roll width against room width — the layout decides this, not a percentage.
How to work out how much carpet to buy
Measure the rectangle, name the roll, then compare the two ways it can be cut.
Measure to the widest point, not around the outline
Carpet is cut as rectangles, so what matters is the largest rectangle the room fits inside. Measure into the doorway, into the closet if it is being carpeted through, and to the deepest point of any bay or bump-out. A room that is 13 ft at one end and 12 ft 9 in at the other is a 13 ft room as far as the cutting table is concerned.
Set the roll width you are actually being sold
Twelve feet is the default for US residential broadloom, some mills weave 15, and imported and commercial goods usually arrive at 13 ft 2 in, which is four meters. This is the input that changes the answer most: a room an inch wider than the roll needs a second cut, a seam and a strip of filler, and none of that shows up in the room's square footage.
Compare the two cutting directions before you accept a quote
The panel lays the room out both ways — cuts running the length and cuts running the width — and shows the running feet and the square feet each costs. Take the leaner one unless the seam it produces would land across the light from the main window or down a walking line, which is the one good reason to buy more material on purpose.
Technical specifications
| Roll widths | 12 ft, 13 ft 2 in (four meters) and 15 ft |
|---|---|
| Layouts compared | Both cutting directions, with running feet, square feet and seam count for each |
| Trim allowance | 3 in on each end of every cut by default, adjustable |
| Seam count | Cuts minus one, worked from the room against the roll width rather than assumed |
| Offcut reporting | Square feet and percent of floor, printed separately — never added into a padded total |
| Stairs | 20 in of running carpet per waterfall tread, cut across the roll so the pile runs down the step |
| Cushion | Listed in square yards as its own line; cushion rolls are 6 ft wide, not 12 |
| Prices | Only the one you type, in either unit, with the nine-times conversion shown both ways |
Frequently asked questions
How wide is a roll of carpet?
Twelve feet, for almost all US residential broadloom. A handful of mills weave 15 ft, which is worth asking for because it takes a 13 or 14 ft room out of a single cut with no seam at all, and most imported and commercial carpet comes at 13 ft 2 in because it is made to a four-meter loom. Nothing else is standard. Carpet tile is the exception to the whole page — it comes in 18 or 24 in squares, is laid like tile and has no roll width to cut around.
Why does a 13 ft wide room cost so much more to carpet than a 12 ft one?
Because the extra foot needs a second cut of the full roll width, and you buy the whole width whether you use it or not. Twelve feet of room takes one cut; thirteen takes two, and the second one supplies a 1 ft filler strip while the remaining 11 ft of its width is offcut. Turning the layout 90 degrees is often the fix — running the cuts across a long room can halve the purchase — which is why the calculator prices both directions rather than picking one.
Is carpet priced per square yard or per square foot?
Both, which is where people get caught, and the two differ by a factor of nine. A carpet at $3.99 per square foot is $35.91 per square yard; a carpet at $35.91 per square yard sounds like four times the price of one at $8.99 per square foot and is in fact half of it. Square yards is the older trade unit and is still what most installers quote in, so always ask which unit a number is in before comparing two of them. Whatever you type here stays in the browser — this is not a quote form and there is no store on the other end of it.
Where should the seam go?
Running the same way as the light from the main window, and out of the walking line. A seam is a line of cut pile butted against cut pile, and light raking across it from the side shows every irregularity in that line while light running along it hides them. Traffic is the other consideration: a seam under a sofa lasts forever and a seam crossing a doorway is the first place the backing lets go. Never seam across a threshold, and never let a seam run in the same direction as a hallway people walk along.
What is pile direction, and why can't the offcut be turned sideways?
Every carpet has a nap — the pile leans one way down the roll — and a piece rotated 180 or 90 degrees reflects light differently enough to look like a different dye lot. It is the same carpet and it will still look wrong, which is why installers mark direction arrows on the back of every piece before cutting. The practical consequence is that a filler strip has to be cut with its pile running the same way as the main piece, so it comes off the roll at full length and cannot be salvaged from a crosswise offcut.
Am I paying for the carpet I do not use?
Yes, and that is the honest answer this page is built to give. The unit of sale is the running foot at full roll width, so the width of a room only changes the bill when it crosses a roll width — below that line the meter stops moving. The offcut is reported here as square feet and as a percentage of the floor rather than folded into a padded total, because a store's quote will be for the material bought, and the only way to check it is against the same figure.
How much carpet does a staircase take?
About 20 in of running carpet per tread on a standard waterfall install — roughly a 7 3/4 in riser plus a 10 in tread plus the wrap over the nosing. What makes stairs cheaper than they look is that the pile has to run down the step, so the pieces are cut across the roll rather than along it: four 36 in wide treads fit side by side across a 12 ft roll, so twelve steps come out of three rows of 20 in rather than twelve separate strips. Capped or upholstered stairs, open risers and pie-shaped winders all take more.
About buying carpet off a roll, and why area is the wrong question
Carpet is roll goods. It is woven on a loom of a fixed width — 12 ft for nearly all US residential broadloom, 15 ft from a few mills, 13 ft 2 in for anything made to a four-meter loom — and it is sold by the running foot off that roll at the full width, used or not. Two consequences follow immediately and neither is visible in a square footage. The first is that any room narrower than the roll costs its own length and nothing else: an 11 ft 6 in room and a 12 ft room take exactly the same carpet off a 12 ft roll. The second is that crossing the roll width is a step change rather than a gradient. A 13 by 20 ft room needs two cuts however you turn it, but cut the long way those are two 20 ft lengths — 480 square feet of roll for 260 square feet of floor, before any trim — and cut the short way they are two 13 ft lengths, 312 square feet, for the same room. The difference is 168 square feet of carpet, bought or not bought on a decision nobody makes explicitly unless they are shown it. That is why this page prices both directions and why it never quotes a waste percentage, and it is the reason carpet has its own tool here rather than sharing the box-counting arithmetic of the flooring calculator.
The constraint that makes the layout rigid is pile direction. Every carpet leans one way down the roll, and a piece rotated to fit reflects light differently enough that it reads as a different color from across a room — not a subtle effect, and not fixable after the fact. Installers mark arrows on the back of every piece for exactly this reason. What it costs you in material is that a filler strip cannot be recovered from a crosswise offcut: it has to come off the roll at full length with its nap aligned, and the rest of that width is scrap. It also means the two cutting directions are genuinely different products rather than the same job rotated, because each puts the seam somewhere different — and a seam wants to run with the light from the main window and away from the walking line, never across a doorway. Where the leaner layout puts the seam in the wrong place, buying the dearer one is the right call, which is a judgement a calculator can inform and should not make. The site’s other roll-goods page, wallpaper, has the same shape of problem with the pattern repeat playing the part that pile direction plays here.
Last, the units. Square yards is the trade unit and square feet is the retail one, they differ by nine, and quotes arrive in both — a $3.99 per square foot carpet is $35.91 per square yard, and a shopper comparing those two figures across two stores without checking the unit will pick the wrong one every time. Cushion is quoted the same way and is a separate order in a different width: cushion rolls are 6 ft, so a room seams the padding more often than the carpet and nobody minds, because a pad seam is taped and never seen. Carpet also has no equivalent of the spare box that a hard floor wants — there is no dye lot to match years later, only the remnant you keep rolled in the garage — which makes the offcut on this page worth actually looking at. Where the room is getting a hard surface instead, the count goes back to pieces and boxes on the tile calculator.
What the store never sees
Every number on this page is worked out by JavaScript running in the tab you are reading it in. Nothing you type — measurements, quantities, the prices your supplier quoted you — is uploaded, logged or kept, which is also why the calculators carry on working on a site with no signal.
The price you were quoted is the most sensitive thing on this page and it is treated the same as the measurements: typed in, used once, and gone when the tab closes.