Carpet comes off a roll of fixed width, so you usually buy more than the room’s floor area. Enter the room size and the roll width; the calculator tries both directions, picks the one that wastes least, and gives the square yards to buy, the seams and the pad.
How to use the carpet calculator
- Measure the room at its longest and widest points, including closets and doorways you will carpet.
- Choose the roll width of the carpet you are buying.
- The result shows the roll length to cut and how many strips, so you can see where the seams fall.
- Pad is laid without a pile direction, so it is estimated from the floor area.
Carpet formula
Strips = room width ÷ roll width, rounded up Roll length = strips × room length Square yards to buy = roll length × roll width ÷ 9 The calculator works this out both ways round and uses the shorter roll length.
Worked example: an 18 × 14 ft room, 12 ft roll
- Laid along the 18 ft side: 14 ÷ 12 = 2 strips × 18 ft = 36 ft of roll.
- Laid along the 14 ft side: 18 ÷ 12 = 2 strips × 14 ft = 28 ft of roll.
- The second way is shorter: 28 × 12 ÷ 9 = 37.33 sq yd, with one seam.
- Pad: 18 × 14 ÷ 9 = 28 sq yd.
Carpet for common room sizes (12 ft roll)
| Room | Floor area | Carpet to buy | Seams |
|---|---|---|---|
| 10 × 10 ft | 11.11 sq yd | 13.33 sq yd | 0 |
| 12 × 12 ft | 16 sq yd | 16 sq yd | 0 |
| 14 × 12 ft | 18.67 sq yd | 18.67 sq yd | 0 |
| 15 × 13 ft | 21.67 sq yd | 34.67 sq yd | 1 |
| 18 × 14 ft | 28 sq yd | 37.33 sq yd | 1 |
| 20 × 16 ft | 35.56 sq yd | 42.67 sq yd | 1 |
Why you buy more than the floor area
A 13 ft wide room on a 12 ft roll needs a second strip just for the last foot, and the rest of that strip is often waste. Installers also match the pile direction across seams, so you cannot simply turn offcuts sideways. Rooms close to the roll width are the most efficient; it is worth checking both roll widths if the carpet comes in more than one.
Questions
How many square yards of carpet for a 12 × 12 room?
16 sq yd on a 12 ft roll, with no seam.
Do I need to add waste?
The roll layout already includes the offcut. Your installer may add a few inches at each wall for trimming; ask for their figure.
How do I convert square feet to square yards?
Divide by 9. The square yard calculator does the conversion for any area.
Sources
- NIST Guide to the SI, Appendix B.8: Factors for units listed alphabetically, National Institute of Standards and Technology.
Used for: Square foot to square yard and metre conversions.