Carpet Calculator
Find how many square yards of carpet you need for a room, plus the estimated cost.
Reviewed by the ToolNestr Editorial Team — July 2026
How the carpet calculator works
Carpet is priced and sold by the square yard, not the square foot, so the first step is finding the room's area in square feet and dividing by 9 (the number of square feet in a square yard). A 15×12 foot room, 180 square feet, needs 20 square yards of carpet before accounting for any waste.
Broadloom carpet comes off the roll in a standard width, most commonly 12 feet. Because carpet can only be cut along its length, not pieced together sideways without a seam, any room wider than the roll width needs at least one seam, and the actual material ordered has to account for that layout rather than just the raw square footage — this calculator flags when your room's width exceeds the standard 12-foot roll.
A waste allowance of 10 to 15% is standard practice to cover trimming at the edges, closets and offsets in the room shape, and pattern matching if the carpet has a repeat. Multiplying the total square yards (with waste) by the price per square yard gives a material cost estimate; padding, if priced separately, and installation labor are typically quoted on top of that material cost.
Roll widths and waste-factor guidance follow Carpet and Rug Institute (CRI 105) installation standards used by residential flooring installers.
Measure the room
Length and width in feet.
Set the waste
10-15% for cuts, pattern matching, offsets.
Order and estimate cost
Square yards, plus a rough material cost.
The formula explained
Room area to sq yd
= (L × W) ÷ 9. A 15×12 ft room: (15×12) ÷ 9 = 20 sq yd.
With waste
× 1.10 = 20 × 1.10 = 22 sq yd to order.
Estimated cost
= sq yd × price. At $35/sq yd: 22 × 35 = $770.
Worked example
A large 20×14 ft family room, 15% waste, $28/sq yd carpet.
Where this calculator gets used
Bedroom recarpeting
Bedrooms are the most common single-room carpet job. Most bedrooms fall under 12 feet in either dimension, so a single length of carpet with no seam is usually possible, which keeps installation simpler and cheaper.
Basement and rec room
Basements and open rec rooms often exceed the 12-foot roll width, requiring one or more seams. Budget extra waste for these rooms, and expect the installer's seam placement to follow furniture layout and light direction.
Stairs and hallways
Stairs need carpet calculated by the tread and riser, not simple area, and hallways are long and narrow — both waste more material proportionally than a square room, so use a higher waste percentage for these areas.
Rental turnover budgeting
Property managers use quick square-yard and cost estimates to budget carpet replacement between tenants, often comparing several rooms at once to prioritize which units need new carpet first.
Real-world context
A standard 11 ft by 13 ft bedroom is a common recarpeting job. That's 143 square feet, or 15.89 square yards raw. With a 10% waste allowance the order comes to 17.48 square yards, and because the room's 13-foot length exceeds the 12-foot roll width, the installer needs a seam — typically placed under a bed or along a wall where it will be least visible underfoot.
A larger 24 ft by 18 ft finished basement tells a different story: 432 square feet, 48 square yards raw, and with a 15% waste allowance (appropriate given the multiple seams a room this size requires) the order grows to 55.2 square yards. At $22 per square yard that's about $1,214 in material alone, before padding and labor — a useful reminder that waste percentage matters more in dollar terms as room size grows.
On the small end, a 4 ft by 10 ft hallway is only 40 square feet, 4.44 square yards raw. With a 12% waste allowance for the narrow, high-cut-loss shape, that's 4.98 square yards, and at $40 per square yard (hallway carpet is often a higher-grade, more durable product) the material cost lands around $199 — small in absolute terms but a good example of why per-project minimums and installer trip charges can dominate the cost of tiny jobs.
Common misconceptions
"I can just divide the room's square footage by 9 and that's exactly how much carpet to buy." Not quite. That raw conversion ignores waste from cutting, pattern matching, and the fact that carpet only comes off the roll in fixed widths — you almost always need to buy more than the bare square-yard figure to actually cover the floor.
"A seam means the installer did a bad job." Seams are normal, not a defect. Any room wider than the standard 12-foot roll requires at least one seam by physical necessity. A skilled installer places seams away from high-traffic paths and door swings and matches pile direction so the seam is barely visible, but it cannot be eliminated on a large room.
Related calculators
Frequently asked questions
How do I calculate how much carpet I need?
Carpet is sold by the square yard, so find the room area in square feet and divide by 9 to convert. A 12×15 ft room (180 sq ft) needs 180 ÷ 9 = 20 square yards, before adding a waste allowance for seams and pattern matching.
Why is carpet sold by 12-foot rolls?
Broadloom carpet is manufactured in standard roll widths, most commonly 12 feet (also available in 13'6" and 15'). Because carpet can only be cut lengthwise off the roll, a room wider than 12 feet needs a seam, which increases the actual material needed beyond the raw square footage.
How much waste allowance should I add for carpet?
A common allowance is 10 to 15% for cutting, pattern matching, and irregular room shapes. Rooms with lots of closets, offsets, or a repeating pattern that must be matched at seams need more waste than a simple rectangular room.
How is carpet cost calculated?
Multiply the total square yards (including waste) by the price per square yard for both the carpet and, separately, the padding underneath it if it is priced separately. Installation labor is usually quoted separately by the installer.
Sources & references
This tool uses standard formulas and reference values from:
- • American Concrete Institute — ACI 318, Building Code Requirements for Structural Concrete. concrete.org
- • ICC — International Residential Code (IRC), span, footing and framing tables. codes.iccsafe.org
- • APA – The Engineered Wood Association, allowable span and load guidance.
Estimates for planning only. Span, load and code values vary by jurisdiction — verify against your local adopted code and a licensed engineer before building.