Wall-to-wall (broadloom) carpet comes off a roll of fixed width, most often 12 feet, with 13½ and 15 ft available for some products. You buy a length of that roll, so the amount you pay for depends on how the room fits the roll, not just on the room's area. A 16 × 14 ft room is 224 ft², but it is wider than a 12 ft roll, so it needs two full-length pieces and a seam, and you pay for about 55% more carpet than the floor area. This carpet calculator lays out full-length pieces both ways across the room, picks the layout that uses the least carpet, and adds the Carpet and Rug Institute's minimum 3 inches of trim along each wall.
For hard flooring sold by the carton, use the flooring calculator. For several rooms, the square footage calculator adds up areas.
How to use the carpet calculator
- Measure the room at its longest and widest points, including closets and doorways that will be carpeted.
- Choose the roll width of the carpet you like. 12 ft is the standard for most residential carpet.
- Keep the trim allowance at 3 inches or more per wall, as CRI 105 requires.
- Enter a price per square yard to compare quotes; carpet is commonly priced by the square yard or square foot.
Formula
The calculator tries the pieces running both ways and keeps the layout with fewer linear feet, preferring fewer seams on a tie. Every piece runs the full length of the room in the same direction, because CRI 105 requires adjacent pieces of the same carpet to have the same pile direction. Installers can sometimes save carpet by filling a narrow strip with offcuts. That adds seams, so this estimate deliberately doesn't count on it.
Worked example
A 16 × 14 ft bedroom with 12 ft carpet and 3 in trim.
- Running along the 16 ft side: (14 + 0.5) ÷ 12 = 1.21, so 2 pieces, each 16.5 ft = 33 linear ft.
- Running along the 14 ft side: (16 + 0.5) ÷ 12 = 1.38, so 2 pieces, each 14.5 ft = 29 linear ft, which is less.
- Order 29 × 12 = 348 ft² = 38.67 yd², with 1 seam.
- The room is 24.89 yd², so about 36% of the carpet is trim and offcut. A 15 ft roll would cover it in one piece: 16.5 × 15 = 247.5 ft² = 27.5 yd², with no seam.
Where seams should go
CRI 105, the Carpet and Rug Institute's residential installation standard, says to keep seams to a minimum. Where possible, seams should run the length of the area, with main traffic running parallel to them rather than across them, natural light not striking across them, and seams kept away from pivoting traffic. Ideally the pile lay faces the entrance. A good installer draws a seaming diagram before ordering. Ask for it when comparing quotes, since two quotes for the same room can differ only in layout. Patterned carpets need extra length for pattern matching, so ask the retailer for the pattern repeat.
Other things to order
Besides the carpet you'll need cushion (pad) to cover the room area, tack strip around the perimeter (the baseboard & trim calculator gives the perimeter), transition strips at doorways to other floors, and, on stairs, roughly a piece per step. Installation is often priced per square yard of carpet installed, and some installers add charges for removing old flooring, moving furniture or stairs. Get the totals in writing.
Caveats and assumptions
- Assumes a rectangular room; for L-shaped rooms, calculate each rectangle separately or ask for a seaming diagram.
- Patterned carpet needs extra for pattern matching, which isn’t included.
- Installers may fill narrow strips with offcuts, using less carpet but adding seams.
- Roll widths vary by product; check before ordering.
Frequently asked questions
How much carpet do I need for a 12 × 12 room?
With 3 in of trim at each wall, the room needs 12.5 ft of width, just over a 12 ft roll. That means 2 pieces of 12.5 ft (33.3 yd²) on a 12 ft roll, or a single piece of a 13½ ft roll (12.5 × 13.5 ft = 18.75 yd²).
How do I convert square feet to square yards of carpet?
Divide square feet by 9. A 224 ft² room is 24.9 yd² of floor, but you’ll order more because of the roll width.
What width does carpet come in?
Most residential broadloom carpet is 12 ft wide; some is made in 13½ or 15 ft widths.
How much extra carpet should I allow?
At least 3 inches along each wall for trimming, as CRI 105 requires, plus whatever the roll width forces. Rooms that don’t fit the roll can waste 30% or more.
Can carpet pieces be turned to save material?
Not for adjacent pieces of the same carpet. CRI 105 requires the pile direction to be the same, so offcuts can only be used in the same direction.
Sources
- The Carpet and Rug Institute — CRI 105 Standard for Installation of Residential Carpet — 3 in trim per wall, seam placement, pile direction
- The Carpet and Rug Institute — Installation Standards — residential and commercial standards
- NIST SP 811, Appendix B — conversion factors — square feet to square meters
This calculator gives estimates for planning and education. Check measurements, local codes, supplier specs and your school's official policy before relying on a result. See our disclaimer and how we build and check calculators.