How much carpet do I need?
Wall-to-wall carpet is cut from a roll, so you buy whole strips the width of the roll, not just the floor area. The installation standard asks for at least 3 in at each wall for trimming, as few seams as possible, and every piece laid with its pile the same way. So a 12 ft roll covers a room up to 11 ft 6 in wide without a seam.
The calculator tries the strips both ways and picks the one with fewer seams, then the one with less carpet. Closets, stairs and L-shaped rooms: work out each rectangle on its own. Patterned carpet needs extra to match the pattern.
Source Carpet and Rug Institute · CRI 105 Standard for Installation of Residential Carpet (sections 5.1 – 5.3) ↗Carpet and Rug Institute · Finding the Right Carpet (broadloom widths) ↗Shaw Floors · Carpet Installation Planning (roll widths) ↗
How to calculate carpet
Here it is with your numbers:
- Floor area, length × width: 14 × 11 = 154 sq ft.
- Add 3 in at each wall for trimming: the carpet must cover 14 ft 6 in × 11 ft 6 in.
- Run the strips along the 14 ft side: 11 ft 6 in across fits 1 strip of the 12 ft roll, cut 14 ft 6 in long.
- The other way, strips along the 11 ft side would take 2 strips and 276 sq ft.
- Carpet to buy, strips × roll width × cut length: 1 × 12 × 14.5 = 174 sq ft.
- Divide by 9 for square yards: 174 ÷ 9 = 19.3333, rounded to 19.33 sq yd.
It means ordering 19.33 sq yd of 12 ft wide carpet: 1 piece 14 ft 6 in long, with no seams.
Carpet is priced by the square yard, which is 9 square feet. The extra over the floor is the price of the roll width: off-cuts from the side of a strip can't be turned to fill a gap, because their pile would run the wrong way.
Carpet for common room sizes
Square yards to order with 3 in at each wall, from a 12 ft roll and from a 15 ft roll.
| Room | 12 ft roll | 15 ft roll |
|---|---|---|
| 10 × 10 ft | 14.00 | 17.50 |
| 12 × 10 ft | 16.67 | 17.50 |
| 12 × 12 ft | 33.33 | 20.83 |
| 14 × 12 ft | 33.33 | 20.83 |
| 15 × 12 ft | 33.33 | 25.83 |
| 16 × 14 ft | 38.67 | 27.50 |
| 20 × 16 ft | 44.00 | 55.00 |
FAQs
How do I calculate how much carpet I need?
Measure the room, add at least 3 in at each wall for trimming, then work out how many strips of the roll cover it. Carpet to buy is strips × roll width × strip length. A 14 × 11 ft room takes one 12 ft × 14 ft 6 in piece: 174 sq ft, or 19.33 sq yd.
What size rolls do carpets come in?
Shaw says most carpet is made in 12 ft rolls, and 15 ft rolls are available too. The Carpet and Rug Institute lists broadloom at 12, 13.5 or 15 ft wide.
Source Shaw Floors · Carpet Installation Planning (roll widths) ↗
What happens if your room is wider than the roll of carpet?
You need a second strip and a seam where they meet. The installation standard asks for as few seams as possible, running along the length of the room, with both pieces' pile laid the same way. A wider roll can avoid the seam.
How do I calculate square yards of carpet needed?
Work out the square feet and divide by 9, because a square yard is 3 ft × 3 ft. 174 sq ft of carpet is 174 ÷ 9 = 19.33 sq yd.
How many yards of carpet is a 12x12 room?
The floor is 144 sq ft, which is 16 sq yd. With 3 in at each wall it's 12 ft 6 in each way, wider than a 12 ft roll: two strips (33.33 sq yd), or one piece from a 15 ft roll (20.83 sq yd).
How much carpet do I need for a 20x20 room?
The floor is 400 sq ft (44.44 sq yd). On a 12 ft roll it takes 2 strips 20 ft 6 in long with one seam: 492 sq ft, or 54.67 sq yd.
Is it normal to see carpet seams?
Yes, a little. The Carpet and Rug Institute says no seam is completely invisible. Seams show least when they run the length of the room and light from windows doesn't fall across them.
Source Carpet and Rug Institute · Frequently Asked Questions (seams) ↗
Sources
- Carpet and Rug Institute: CRI 105 Standard for Installation of Residential Carpet (sections 5.1 – 5.3)
- Carpet and Rug Institute: Finding the Right Carpet (broadloom widths)
- Shaw Floors: Carpet Installation Planning (roll widths)
- Carpet and Rug Institute: Frequently Asked Questions (seams)
- NIST Handbook 44 (2026): Appendix C, General Tables of Units of Measurement (1 square yard = 9 square feet)