Carpet Calculator
Square yards from the room and the roll width, counted in strips because the roll is, with stairs, waste and an optional installed price.
Square yards to buy from the room and the roll width — which is what decides the cut, not the area — plus stairs, waste and an optional cost per yard.
| Floor area | — |
|---|---|
| Strips off the roll | — |
| Carpet for the room | — |
| Stairs | — |
| Order with waste | — |
| Cost | — |
Carpet is cut from a 12-foot roll, and that is why the area is the wrong number. A 12 × 15 room is 180 ft², 20 square yards, and takes exactly one 15-foot strip off a 12-foot roll: 20 yards, no waste. A 13 × 15 room is 195 ft² but takes two strips — the second one 15 feet long and a foot wide — so it is 40 yards off the roll unless the installer can seam the offcut. The calculator counts strips, not square feet, because the roll does.
Square yards, because that is how it is sold. Nine square feet to the yard. Quotes per square foot exist and are the same price divided by nine; the page prints both.
Stairs take more than their tread. Each step wraps the tread and the riser, about 18½ inches of run per step on a standard stair, and is cut the width of the stair. Thirteen steps at 36 inches wide are about 6½ square yards; a runner is less, a wider stair more.
Waste is seams and pattern. A plain carpet in a rectangle can run near zero once the strips are counted; a patterned carpet has to match at every seam, and rooms with alcoves and closets eat offcuts. 10% is the usual allowance on top of the strip count.
Strips = ceil(room width ÷ roll width), laid the length of the room; carpet bought = strips × roll width × room length ÷ 9. Stairs = steps × (tread + riser) × stair width ÷ 9. Waste is applied to the total. Roll widths are the common 12 ft, 13 ft 6 in and 15 ft; the price is yours.
Worked example
A 15 × 12 ft room off a 12-foot roll: how much carpet?
- 180 ft² is 20 square yards — but the roll decides: 12 ft wide, so one strip 15 ft long covers the room.
- 12 × 15 ÷ 9 = 20 yd² off the roll, no seam and no offcut.
- With 10% waste, 22 yd²; add 13 stairs at 36 in and it is 29.35.
22 square yards for the room alone. A 13 ft wide room in the same length would take two strips — 40 yards — which is why this page counts strips, not square feet.
Questions
How many square yards of carpet for a 12 × 15 room?
20 — 180 ft² ÷ 9 — and because the room is exactly one 12-foot roll width, one 15-foot strip covers it with no seam.
How wide is a roll of carpet?
12 feet is the common broadloom width; 13 ft 6 in and 15 ft are also made. The width decides how many strips a room takes, which is what you pay for.