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.
Quick answer: carpet you pay for, by roll width
| Room | 12 ft roll | 13 ft 6 in roll | 15 ft roll |
|---|---|---|---|
| 10 × 12 ft | 16 yd² | 18 yd² | 20 yd² |
| 12 × 12 ft | 16 yd² | 18 yd² | 20 yd² |
| 12 × 15 ft | 20 yd² | 22.5 yd² | 25 yd² |
| 13 × 16 ft | 42.67 yd² | 24 yd² | 26.67 yd² |
| 14 × 18 ft | 48 yd² | 54 yd² | 30 yd² |
| 16 × 20 ft | 53.33 yd² | 60 yd² | 66.67 yd² |
Carpet is bought in whole strips along the long side: strips × roll width × length ÷ 9. A 13 × 16 room overruns a 12 ft roll and pays for two strips. No stairs, no waste.
| 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 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.
The pile has a direction, and the standard says every piece runs the same way. CRI 105, the Carpet and Rug Institute's residential installation standard, requires adjacent pieces of the same broadloom to have the same pile direction (§5.2), and suggests laying the pile toward the entrance. An offcut is a usable fill only if it can lie the same way as the strip beside it; turned 90° it shades differently and the standard does not allow it. That is why a leftover of the right size is not always a usable one, and why this page counts strips laid the length of the room.
Where the seams go is a requirement, not a taste. §5.1: keep seams to a minimum and run them the length of the area, with the main traffic parallel to them, out of light that strikes across them, away from pivoting traffic and not perpendicular to a doorway. A room that only fits the roll with a seam across its door is a room to lay the other way, even when that costs a strip.
Four more numbers from the same standard. A power stretcher is mandatory (§11.4), and tufted carpet on a synthetic backing is stretched at least 1% in length and in width unless the maker says otherwise (§11.5). Residential cushion should not exceed 7/16 in. (11 mm) (§11.2). Carpet and materials acclimate at least 24 hours at 65 to 95 °F (18 to 35 °C) before installation (§9.0). On stairs, the standard notes that most manufacturers want the pile running down the stairs.
What I check on a job
Where the seam lands decides the order. Before I trust this number, I measure the width at both ends of the room, because the strip count turns on it. A room that measures exactly 12 feet at one wall and a little more at the other is a two-strip room, and the calculator only knows that if I give it the larger figure. The page lays strips along the longer side to keep seams down, but what I check is where the seam lands. Across a doorway or down the middle of the main path is where a seam shows first and wears first, and I would rather pay for the extra yardage of running the strips the other way than put one there. Closets and halls I enter as their own rooms, because the offcut warning only sees one rectangle; then I check whether the main room's offcut covers them. I read the installer's yardage against the strip count. If it matches the floor area instead, someone has assumed a seam I have not agreed to.
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.
11 values on this page were driven in a browser and compared with independently derived figures on 2026-10-29 (2808 values across 228 calculators site-wide).
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.
How much carpet does a 13 × 15 ft room take?
Two strips off a 12 ft roll, the second 15 ft long for a one-foot gap: 40 square yards bought for 195 ft² of floor, unless the installer can seam the offcut. A 12 × 15 room takes one strip, exactly 20 square yards. The roll, not the area, sets the order.
How much carpet do 13 stairs take?
About 6½ square yards at 36 in. wide: each step wraps the tread and the riser, about 18½ in. of run on a standard stair, cut the width of the stair. A runner takes less and a wider stair more.