Carpet Calculator
Multiply room length by width for area, then add roughly 15% extra to account for carpet’s standard 12-foot roll width and seam waste, and convert to square yards since carpet is often priced that way.
Quick Answer
Multiply room length by width for area, then add roughly 15% extra to account for carpet’s standard 12-foot roll width and seam waste, and convert to square yards since carpet is often priced that way.
Carpet Calculator
Enter your values below for an instant result, then see the formula, worked example, and common mistakes.
Enter your values and click calculate.
How to Use This Calculator
Measure length and width in feet for the full area to be carpeted, including closets.
Carpet ships in wide rolls (commonly 12 feet). If your room doesn’t divide evenly into that width, you’ll have leftover waste on every cut — this is why carpet waste factors run higher than tile or plank flooring.
Carpet is frequently priced per square yard in the US, not per square foot. 1 square yard = 9 square feet.
Padding plus professional installation commonly adds $1-$4+ per square foot on top of the carpet material itself.
Formula
Carpet needed (sq ft) ≈ Length x Width x 1.15 (accounts for 12 ft roll-width seam waste). Divide by 9 for square yards.
Reference Table: Carpet Waste Factor by Room Shape
| Room shape | Typical waste factor |
|---|---|
| Simple rectangular room, width close to roll width | 10-13% |
| Standard rectangular room | 13-15% |
| L-shaped room, hallway, or many small rooms | 15-20% |
| Patterned carpet needing match-up | 20%+ |
Common Mistakes to Avoid
- Assuming carpet waste is the same as flooring waste (5-10%) — carpet’s fixed roll width usually pushes real waste closer to 15-20%.
- Confusing square feet and square yards when comparing quotes — always check which unit a price is quoted in.
- Forgetting stairs, which use roughly 12-15 square feet of carpet per step including tread, riser, and nosing wrap.
- Not budgeting separately for padding, which is priced and replaced separately from the carpet itself.
When the Estimate May Be Wrong
Actual waste depends heavily on room shape and carpet roll width (12 ft is most common, but 13 ft 2 in and 15 ft rolls exist). Irregular rooms, hallways, and stairs typically need a professional measure for an exact cut plan — this calculator gives a budgeting estimate, not a cut sheet.
FAQs
Is carpet priced by the square foot or square yard?
Both are used, but square yard is the more traditional US carpet industry unit; 1 square yard equals 9 square feet.
Why does carpet need more waste than other flooring?
Carpet comes in fixed-width rolls (commonly 12 feet), so any room dimension that doesn’t divide evenly into that width creates offcut waste on every seam.
How much carpet do I need for stairs?
Budget about 12-15 square feet per step to cover the tread, riser, and nosing wrap.
Sources and Methodology
Waste-factor guidance reflects commonly published carpet industry figures (13-20% typical, cited by flooring retailers and installers) based on standard 12-foot carpet roll widths, current as of 2026.
