How this calculator works
Carpet is woven in wide rolls, usually 12 ft wide and sometimes 15 ft. You order a length off the roll, and you pay for the full width however much of it you use. So the question is how many strips as wide as the roll you need to cover the floor, and how long each must be. A strip can run along the room's length or along its width, so we try both and take the one that needs less carpet.
Worked example: a 15 × 12 ft room on a 12 ft roll. Running strips along the 15 ft side, the 12 ft width is covered by one strip, so you order 15 ft + 3 in of trim = 15.25 ft, which is 183 ft² (20.3 yd²) for a 180 ft² floor. Running them the other way would need two strips of 12.25 ft, or 24.5 ft, so the first layout wins.
Carpet to order for common room sizes (3 in trim per strip)
Length off the roll, using the better direction. Compare the wide roll when a room is just over 12 ft in one direction.
| Room | 12 ft roll | 15 ft roll |
|---|---|---|
| 10 × 10 ft | 10.25 ft | 10.25 ft |
| 10 × 12 ft | 10.25 ft | 10.25 ft |
| 12 × 12 ft | 12.25 ft | 12.25 ft |
| 12 × 15 ft | 15.25 ft | 12.25 ft |
| 12 × 18 ft | 18.25 ft | 18.25 ft |
| 14 × 16 ft | 28.50 ft | 16.25 ft |
| 14 × 20 ft | 28.50 ft | 20.25 ft |
| 16 × 20 ft | 32.50 ft | 32.50 ft |
Tips before you buy
- A room just wider than the roll is expensive: a 13 ft width on a 12 ft roll needs a second strip, a seam, and a lot of cutoff. Check the 15 ft roll before you accept that, and ask the store which they would use.
- Run the pile the same way in every strip, and put seams where they are least seen and walked on: away from doorways and across the direction of the light from windows.
- Buy everything from the same dye lot and the same roll. Colors vary between runs, and an extra piece ordered later may not match.
- Patterned carpet wastes more: each strip has to start at the same point in the pattern, so allow one full pattern repeat extra for each strip.
- Measure to the widest points of the room, including into doorways and closets, and let the installer check your numbers before the order is cut.
- Pad is bought by the square yard and cut to fit, so it does not need seams to match. Budget a little for tack strip, seam tape and transitions too.
Tools & materials for this project
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Frequently asked questions
How much carpet do I need for a 12x12 room?
On a 12 ft roll, one strip of 12 ft plus about 3 in for trimming: 12.25 ft, which is 147 ft² or 16.3 yd² of carpet, for a floor of 16 yd².
How do I calculate square yards of carpet?
Multiply the length by the width in feet to get square feet, then divide by 9. A 15 × 12 ft room is 180 ft², or 20 yd². You will usually pay for more, because carpet is sold in full-width strips off the roll.
Why is the carpet I have to buy more than my floor area?
Because the roll is a fixed width. If the room is 13 ft wide and the roll 12 ft, you need two strips and cut one down. The cutoff is yours, but you have paid for it.
How much extra carpet should I order?
Around 3 in per strip for trimming, which the calculator adds. Add a pattern repeat per strip for a patterned carpet, and ask for a little extra if the room has bays, angles or stairs.
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Estimates only. Results assume standard materials and simple shapes. Supplier products vary, and the final call on quantity, structure and safety is yours. Check your local code and your supplier's guidance before ordering.