Carpet Calculator
Calculate how much carpet to order in linear feet of roll and square yards, based on the room size and a 12, 13.5 or 15 ft roll width, plus padding and cost.
By CalcBuilt Editorial TeamUpdated September 9, 2026Formulas checked against manufacturer specs, see how we calculate.
Results
- Carpet to order
- 11 ft of 12 ft wide roll
- 1 run of 10 ft laid along the room's width, plus 10% waste
- Carpet area
- 14.67 sq yd
- 132 sq ft of carpet
- Floor area
- 13.33 sq yd
- 120 sq ft
- Padding
- 13.33 sq yd
- Pad is seamed anywhere, so buy the floor area. Standard is 7/16 in (11 mm) thick, 6 lb density
Carpet formula
Runs = Room width / roll width, rounded up (also try Room length / roll width)
Linear feet of roll = Runs x run length, using the orientation with less carpet
Order length = Linear feet x (1 + waste %), rounded up to a whole foot
Square yards = Order length x roll width / 9Worked example
A 15 x 18 ft living room on a 12 ft roll: runs across the 15 ft width need 2 runs of 18 ft = 36 ft, while runs across the 18 ft length need 2 runs of 15 ft = 30 ft. Take 30 ft, add 10% for 33 ft. 33 x 12 = 396 sq ft, or 44 sq yd. The floor itself is 270 sq ft, or 30 sq yd, so 30 sq yd of pad. At $25 per sq yd the carpet costs $1,100.
On a 15 ft roll the same room needs one 18 ft run with no seam. With waste that is 20 ft, or 300 sq ft (33.3 sq yd), which saves 10.7 sq yd and the seam.
Quick reference
| Room size | Floor area | Roll length | Carpet to buy |
|---|---|---|---|
| 10 x 10 ft | 11.11 sq yd | 11 ft | 14.67 sq yd |
| 10 x 12 ft | 13.33 sq yd | 11 ft | 14.67 sq yd |
| 12 x 12 ft | 16.00 sq yd | 14 ft | 18.67 sq yd |
| 12 x 15 ft | 20.00 sq yd | 17 ft | 22.67 sq yd |
| 14 x 16 ft | 24.89 sq yd | 31 ft | 41.33 sq yd |
| 15 x 20 ft | 33.33 sq yd | 33 ft | 44.00 sq yd |
| 20 x 20 ft | 44.44 sq yd | 44 ft | 58.67 sq yd |
How to calculate carpet
Carpet comes off a roll, almost always 12 feet wide, so you buy a length of roll rather than the exact floor area. Divide the room's narrow dimension by the roll width and round up to get the number of runs, then multiply by the other dimension for the length of roll. A 10 by 12 foot room fits in one 10 foot run of 12 foot roll.
When a room is wider than 12 feet, check both directions. A 14 by 16 foot room needs two 16 foot runs (32 feet) laid one way but two 14 foot runs (28 feet) laid the other. The second run is cut into fill strips, and every fill must run the same direction off the roll as the main piece. A closet gets a fill from that run, never a scrap turned sideways. Patterned carpet needs a full pattern repeat added to every cut piece so it matches across the seam; a 36 inch repeat can push waste to 20 percent.
Padding, seams and square yards
Carpet stores quote by the square yard, which is 9 square feet, and you pay for roll yards, not floor yards. Pad comes in 6 foot rolls of 30 square yards and is seamed anywhere, so order pad for the floor area only. For residential cut pile, CRI 105 calls for pad no thicker than 7/16 inch at 6 lb density or better. Berber and loop pile get 3/8 inch or less at 8 lb. Thicker or softer pads let the carpet flex, break the latex backing and open the seams.
Plan seams to run with the length of the room and with the light from the main window, out of doorways and traffic lanes. Residential carpet is a stretch-in job: tack strip around the perimeter, pad stapled or glued inside it, seams hot-melt taped, then the carpet power-stretched and tucked. CRI 105 does not accept a knee kicker alone. Glue-down is for basements, commercial floors and wheelchair use, and on a slab it needs a moisture test first (CRI 104). If a 13.5 or 15 foot width is made in your style, it removes the seam in a bedroom or living room and often costs less overall. It is special order, with a 2 to 4 week lead.
What this calculator leaves out
Carpet and pad only. Not included: tack strip (4 foot sticks, one per 4 feet of perimeter, concrete-pin on slabs), seam tape, and a metal or vinyl transition at every doorway. Stairs are figured separately: a straight 3 foot wide stair with 13 steps takes about 7 feet of 12 foot roll, and wrapped or pie steps take more. Removing and hauling the old carpet and pad, and moving furniture, are labor line items. Installers charge by the square yard plus per-step and per-transition fees, so get the labor quote in writing with the same yardage as the carpet order.
Mistakes that cost money
- Buying by floor area: a 14 x 16 room is 25 sq yd of floor but takes 41 sq yd off a 12 ft roll.
- Fill pieces laid with the pile turned read as a different color at the seam; every piece runs the same direction off the roll.
- A seam across a doorway or traffic lane peaks and frays; run seams with the room's length and the light, never through a doorway.
- Thick soft pad under berber lets the loops flex and seams open; berber and loop pile need 3/8 in or thinner at 8 lb.
- Stretching with a knee kicker alone leaves the carpet loose and it ripples in a year; CRI 105 requires a power stretcher on every room.
- Tack strip set farther from the wall than the carpet thickness leaves an edge that will not tuck; on a slab use concrete-pin strip.
Key facts
- Carpet is sold from 12 ft wide rolls; 13.5 and 15 ft widths are made for some styles and can eliminate a seam.
- One square yard is 9 sq ft. A 12 x 12 ft room is 16 sq yd of floor but needs about 18.67 sq yd of carpet.
- Residential cut-pile carpet needs a pad no thicker than 7/16 in with at least 6 lb density; berber and looped carpet needs 3/8 in or less at 8 lb.
- Seams should run the length of the room, parallel to the light from the main window so they cast no shadow, and never across a doorway.
- Rooms wider than the roll always need a seam, so ordering the run direction that leaves a strip of usable width cuts waste.
Frequently asked questions
How much carpet do I need for a 12x12 room?
One 12 ft run of 12 ft wide roll, or about 14 ft with 10% waste. That is 168 square feet, or 18.67 square yards, for a floor of 16 square yards.
How do I convert carpet square feet to square yards?
Divide square feet by 9. A 300 square foot room is 33.3 square yards. Carpet stores price per square yard, though some now quote per square foot.
Do I need new padding when I replace carpet?
Almost always. Old pad is crushed in the traffic lanes and holds pet odor, and most carpet warranties require new pad that meets their density and thickness spec. Pad is a small share of the job, typically $4 to $10 per square yard at 2026 US retail. Tack strip can stay if it is not rusted or loose.
How much extra carpet should I order?
About 10% beyond the roll math for trimming and seam allowance, or 15% for patterned carpet. The calculator already accounts for the roll width, which is the biggest source of extra material.
Sources and references
- Carpet installation guide: 12 and 15 ft rolls, seams and cushion (Shaw Floors)
- CRI 105 Standard for Installation of Residential Carpet (Carpet and Rug Institute)
- Carpet installation standards CRI 104 and 105 (Carpet and Rug Institute)
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Results are estimates based on standard formulas and typical product specifications. Confirm quantities with your supplier and local code before ordering.