Flooring & Tile
Carpet Calculator
Square yards of carpet and padding for a room, accounting for standard 12 ft roll widths and seams.
Inputs
Results
Adjust the inputs to see your result.
About this calculator
Carpet comes on rolls, usually 12 ft wide, so the amount you buy rarely equals the area of the room — the offcut from the roll width is part of the maths. This calculator works out the linear feet to order, the square yards it represents, and the padding to match.
What this number means
Carpet is the one floor covering where the room area is not the buying figure. Because it comes off a roll of fixed width, you buy whole runs: any part of the roll's width that does not land on your floor is still on your invoice. A room slightly wider than the roll forces a second run and a seam, and that second run is bought at full roll width even if only a narrow strip is used.
Direction matters for the same reason. Running the carpet the other way can drop a whole seam — the calculator tests both orientations and reports the cheaper one, plus the padding area (padding is cut to the room, so it follows the true room area, not the roll).
The formula
- Runs = Room width across the roll ÷ roll width, rounded up
- Linear feet to order = Runs × room length along the run
- Purchased area = Linear feet × roll width (sq ft), and square yards = purchased sq ft ÷ 9
- Both orientations are computed; the one with the smaller purchased area wins. Seams and pile direction are noted in the result.
- Padding = true room area ÷ 9 sq yd, rounded up to the next half yard.
Worked example
A bedroom that fits the roll exactly. The room is 15 ft long × 12 ft wide and the carpet is on a standard 12 ft roll.
- Runs across the 12 ft width = 12 ÷ 12 = 1 run — no seam at all
- Linear feet = 1 × 15 ft = 15 linear ft
- Purchased = 15 × 12 = 180 sq ft = 20 sq yd
- Padding follows the room: 180 sq ft = 20 sq yd
Now widen the room to 14 ft and watch what happens: a second run appears, purchased area jumps, and rotating the carpet the other way becomes the cheaper option — the calculator shows both.
Assumptions and limitations
- Seamed strips are priced at full roll width, which is how most retailers sell cut carpet. A few will sell a part-width fill piece; if yours does, your bill can be lower than this estimate.
- Pile direction must run the same way on every piece for the colour to match. The calculator assumes the winning direction also works for pile — if the room has strong directional light, an installer may insist on the other orientation.
- Patterned carpet needs extra length for pattern matching between runs; add roughly one pattern repeat per seam, which this estimate does not include.
- Stairs, landings and closets are calculated as separate rooms.
Frequently asked questions
Because carpet is cut from a roll of fixed width. If your room is 13 ft wide and the roll is 12 ft, you buy two runs and the second run is charged at the full 12 ft width even though only a 1 ft strip lands on the floor. The purchased area — not the room area — is what you pay for.
Divide square feet by 9. A 180 sq ft purchase is 20 sq yd. Most US carpet pricing is per square yard, so this is the figure to compare quotes with.
Yes. The number of runs depends on which room dimension crosses the roll. A 12 × 15 ft room needs one run in one direction and two in the other — the calculator tests both and keeps the cheaper, seam-count included.
Padding is cut to fit the room rather than the roll, so it follows the true room area: room square feet ÷ 9, rounded up. The result panel shows it separately from the carpet figure.
Seams should run parallel to the main light source and away from the heaviest traffic line where possible — never directly in a doorway threshold if it can be avoided. If the cheaper direction puts a seam in a bad place, the installer may override it; the material difference is usually small.