Carpet Calculator: How Much Carpet Do I Need?
Work out how much carpet a room needs from 12 or 15 ft roll widths, with seams, waste, padding and the installed cost. Add each room and the stairs, pick the roll width, and take the square yards and linear feet to the supplier or the quote.
Your numbers
Rooms
Up to 8 rectangles. Split an L-shaped room into two; each is laid on its own.
Roll and layout
12 ft is the usual width; some carpets come 13.5 or 15 ft wide.
All strips in a room run the same way, so the pile matches.
The CRI installation standard allows at least 3 in at each wall, so 6 in a strip.
Stairs
Pad and prices
Optional. Applied to the carpet ordered.
Carpet to order
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- Length off a 12 ft roll
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- Floor area
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- Waste
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- Seams
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- Pad
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- Carpet
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- Pad
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- Installation
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- Installed cost
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A single-room layout estimate. An installer plans a seaming diagram for the whole job and can cut fills from offcuts, so the real order can be smaller.
Seam placement, stretching and the pad follow the carpet maker's instructions and the installer's plan.
The calculation runs in your browser and ParrotNotes does not store your numbers. They sit in the page address so you can bookmark or share the result.
Why carpet is ordered by the roll, not by the floor
Wall-to-wall carpet comes off a roll of one width: 12 ft is the usual width, and some carpets also come 13.5 or 15 ft wide. So a room is covered in strips as wide as the roll. Divide the room's width by the roll width and round up for the number of strips; each strip is the room's length plus a few inches for trimming at the walls. The order is that length of roll, and the square yards are length × roll width ÷ 9.
Worked example: a 15 × 12 ft bedroom is 180 sq ft, or 20 sq yd. On a 12 ft roll it takes one strip of 15 ft 6 in: 186 sq ft, or 20.67 sq yd, about 3 % waste and no seam. A 15 × 14 ft room on the same roll needs two strips either way: two of 15 ft 6 in along the length is 31 ft of roll, two of 14 ft 6 in across it is 29 ft. The calculator tries both and shows the one with less carpet unless you pick a direction.
Seams and pile direction
The Carpet and Rug Institute's residential installation standard, CRI 105, says to keep seams to a minimum, to run them the length of the area where possible, with the main traffic parallel to the seam rather than across it, and to keep them out of light that strikes across them. Where two pieces of the same carpet meet, the pile direction has to be the same. That is why the calculator never turns a piece to fit an offcut into a room.
CRI 105 also calls for at least 3 inches along each wall for trimming, so the calculator adds 6 inches to every strip by default. It lays each room on its own: an installer drawing a seaming diagram for the whole job can cut closets and small fills from offcuts, so the real order can be smaller.
Carpet on stairs
Each step takes a piece as wide as the stair and long enough for the tread, the riser and the wrap over the nose. CRI 105 recommends the length of the carpet run down the stairs, and notes that most makers want the pile to run down them, so the calculator cuts step pieces side by side across the roll. A 3 ft wide stair fits four pieces across a 12 ft roll.
The stair width (3 ft) and the carpet per step (18 in) are typical starting values, not a standard: measure the actual stair, including any landing, and edit them.
Tips for the site visit
Measure every room at its widest point, closets included, and sketch where the doorways are: seams that run into a doorway or across a hallway are the ones customers notice. Note the floor that has to come up, the tack strip, the furniture to move and the transitions to hard floors.
Then write down what the customer told you: the carpet and pad they chose, where they will and will not accept a seam, which rooms are done first and the install date. Those notes decide the quote as much as the yardage does.
Sources, checked October 2026. All figures are estimates:
More for flooring, home-services and building-materials sales: Door-to-door sales, Building materials sales, Construction daily report.
Where the seams go is a conversation, not a number
The yardage goes on the quote. What the customer said on the walk-through about the carpet and pad they picked, where a seam may and may not go, the furniture to move, the stairs and the install date goes in ParrotNotes: record the visit and get the summary and next steps.
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