How this calculator works
Carpet comes off a roll of fixed width, so you pay for whole strips, not just the room area. The calculator tries running the strips both ways, adds a trim allowance per strip, and picks the layout that uses less carpet.
Strips = round up( Room dimension across ÷ Roll width )
Linear ft = Strips × (Room dimension along + Trim)
Square yards = Linear ft × Roll width ÷ 9
Assumptions and tips
- Pile direction must match across seams, which may force a less efficient layout.
- Pattern matching, stairs and closets add material; ask your installer to confirm.
Worked example
Using the default values in the calculator above:
| Input | Value |
|---|---|
| Room length | 15 ft |
| Room width | 13 ft |
| Roll width | 12 ft |
| Trim allowance per cut | 6 in |
| Price per sq yd (optional) | $0 |
| Result | Value |
|---|---|
| Carpet to buy | 36 sq yd |
| Length off the roll | 27 linear ft |
| Strips (seams = strips − 1) | 2 strips |
| Room area | 21.7 sq yd |
Step by step:
- Strips across the width: 2 × (15 + 0.5) = 31 linear ft
- Strips across the length: 2 × (13 + 0.5) = 27 linear ft
- Use the smaller: 27 ft × 12 ft ÷ 9 = 36 sq yd
Carpet needed on a 12 ft roll
6 in trim allowance per strip.
| Room | Carpet to buy | Room area |
|---|---|---|
| 10 × 12 ft | 14 sq yd | 13.3 sq yd |
| 12 × 12 ft | 16.7 sq yd | 16 sq yd |
| 12 × 15 ft | 20.7 sq yd | 20 sq yd |
| 13 × 15 ft | 36 sq yd | 21.7 sq yd |
| 14 × 18 ft | 38.7 sq yd | 28 sq yd |
Common mistakes to avoid
- Comparing quotes on room area when you pay for the roll width.
- Placing seams in high-traffic doorways.
Frequently asked questions
Why is the carpet bigger than my room?
Rolls come in set widths. A 13 ft wide room on a 12 ft roll needs a second strip, and you pay for the whole width of both.
How do I convert square feet to square yards?
Divide by 9.