How to use the carpet calculator
- Measure each room. Measure the longest length and width wall to wall, into doorways, and round up to the next half foot. Leave room 3 at 0 if you only have one or two rooms.
- Choose the roll width. Most broadloom carpet comes in 12 ft rolls; some is 15 ft or 13.5 ft. A room narrower than the roll can be done with no seam.
- Keep the trim allowance. Installers add about 3 in at each end of a cut, so 6 in per strip is standard.
- Add prices. Carpet is priced per sq ft or per sq yd (9 sq ft). Pad and installation are usually priced per sq ft of room.
Carpet formulas
Square yards = square feet ÷ 9
Strips = room width ÷ roll width (round up)
Roll length = strips × (room length + trim)
Carpet to order = roll length × roll width
The calculator tries both directions for every room and keeps the one that uses less carpet. Pattern matching and seams in high-traffic areas can change the best layout, so let your installer confirm.
Worked example
A 14 × 12 ft bedroom and a 12 × 11 ft bedroom cover 168 + 132 = 300 sq ft, or 33.3 sq yd. From a 12 ft roll the first room is one strip 14.5 ft long and the second is one strip 11.5 ft long. That is 26 ft of roll, or 312 sq ft (34.7 sq yd) to order, only 4% waste and no seams. You also need about 315 sq ft of pad.
Carpet cost guide
| Item | Typical price |
|---|---|
| Carpet, budget to mid-range | $1.50 - $4.00 per sq ft |
| Carpet, premium wool or nylon | $5 - $12 per sq ft |
| Carpet pad | $0.40 - $1.00 per sq ft |
| Installation | $0.75 - $2.00 per sq ft |
| Old carpet removal | $0.25 - $0.50 per sq ft |
Typical 2025-2026 US prices. Stairs are usually priced per step. For hard flooring use the tile calculator or the square footage calculator.
Frequently asked questions
How do I calculate how much carpet I need?
Multiply the room length by the width to get square feet, and divide by 9 for square yards. Then work out how many strips of the roll width fit across the room and add about 6 in of trim to each strip.
How many square yards of carpet do I need for a 12 x 12 room?
A 12 × 12 room is 144 sq ft, or 16 sq yd. Cut from a 12 ft roll with 6 in of trim, you order 12.5 ft of roll, which is 150 sq ft or 16.7 sq yd.
How much extra carpet should I buy?
Usually 5% to 10% over the room area. Rooms wider than the roll, odd shapes and patterned carpet need more, sometimes 15% to 20%.
How much does it cost to carpet a 12 x 12 room?
With mid-range carpet at $3 per sq ft, pad at $0.60 and installation at $1.25, a 12 × 12 room costs about $720 all in: $450 carpet (150 sq ft cut from the roll), $91 pad and $180 installation.
Do I need carpet padding?
Yes. Pad makes carpet softer, quieter and warmer and protects the backing, and most carpet warranties require an approved pad.
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Last updated October 2026.