Calculate how many square yards of carpet you need for any room, plus the linear feet of 12-foot-wide roll to order, with a waste factor. Free carpet calculator for contractors.
Enter the room length and width, then pick a waste factor. The calculator figures the total square footage to order (with waste included), converts it to square yards — how carpet is sold — and estimates the linear feet of 12-foot-wide roll you need to buy.
What this carpet calculator estimates
The carpet calculator estimates the amount of carpet required to cover a single rectangular room and converts that area into the two quantities you actually order by: square yards (how carpet is priced) and linear feet of a 12-foot-wide roll (how carpet is cut from the bolt). It also reports the total square footage to order with your waste factor already applied, plus the net floor area so you can cross-check against your tape measure. Enter the room length and width in feet, pick a waste factor, and the tool returns square yards, linear feet of roll, and total square feet.
How to measure and enter each input
Measure the room length (feet): the longer floor dimension, wall-to-wall at the baseboard. Measure to the longest point, including any alcove or closet that will be carpeted.
Measure the room width (feet): the perpendicular floor dimension, also wall-to-wall.
Pick a waste factor: 5% for a simple open room with a straight lay and few cuts; 10% (standard) for a straight lay in a typical rectangular room; 15% for rooms with closets or many angles; 20% for patterned carpet that must be matched across seams.
Square yards — how carpet is sold
Carpet is priced and ordered by the square yard. Because one square yard equals 9 square feet (3 ft × 3 ft), you convert square feet to square yards by dividing by 9. The calculator applies your waste factor to the net floor area first, then divides by 9, so the square-yard figure already includes your cuts and seaming allowance.
Roll width and linear feet
Carpet comes on a bolt in a fixed width — most commonly 12 feet, with 15-foot goods available for wider rooms and fewer seams. The calculator divides the total square footage by 12 to estimate the linear feet of 12-foot-wide roll you need to buy, rounded up to the next whole foot. If your supplier stocks 15-foot goods, divide the total square footage by 15 instead.
For rooms wider than the roll, the installer seams two widths together. The waste factor covers the overlap and seaming loss, so you do not need to add it separately — but patterned carpet with a repeat may need a higher waste factor (20%) to line up the design across the seam.
Waste factors for carpet
Straight lay, rectangular room: 10% — the standard. Use 5% only for a simple open room with very few cuts.
Rooms with closets, angles, or many cuts: 15% — bump up from the straight-lay default.
Patterned carpet (matched across seams): 20% — the pattern repeat forces extra cuts to line up the design.
Stairs: 15–20% — many angled cuts with little reusable offcut. Measure tread and riser of one step and multiply by the number of steps.
Formulas and units
Net area = length × width (square feet).
Total sq ft to order = net area × waste factor, rounded to the nearest square foot.
Square yards = total sq ft ÷ 9, rounded up to the next whole square yard.
Linear feet of 12-ft roll = total sq ft ÷ 12, rounded up to the next whole foot.
Roll width is assumed to be 12 ft — divide by 15 instead if you order 15-foot goods.
Worked example
Carpet a 20 ft × 15 ft room with a 10% waste factor — the calculator’s default values:
Net area = 20 × 15 = 300 sq ft.
Total sq ft to order = 300 × 1.10 = 330 sq ft.
Square yards = 330 ÷ 9 = 36.7, rounded up to 37 square yards.
Linear feet of 12-ft roll = 330 ÷ 12 = 27.5, rounded up to 28 linear feet.
Net area reported = 300 sq ft.
The calculator displays 37 square yards, 28 linear feet of 12-foot roll, and 330 sq ft to order — matching the math above. Because the room is 15 ft wide and the roll is 12 ft wide, the installer will seam a 3-ft strip along one edge; the 10% waste factor covers that overlap.
Common mistakes
Ordering by square feet instead of square yards — carpet is sold by the square yard (9 sq ft), so dividing by 9 is essential.
Using a 10% straight-lay waste factor on patterned carpet and running short on the seam match.
Assuming every roll is 12 ft wide — 15-foot goods exist and cut the seam count on wide rooms.
Forgetting to add waste for stairs, where angled cuts create many small offcuts.
Treating an L-shaped or irregular room as a single rectangle — break it into separate rectangles and add the totals.
Frequently asked questions
How many square feet are in a square yard of carpet?
One square yard equals 9 square feet (3 ft × 3 ft). To convert square feet to square yards, divide by 9. The calculator does this automatically after applying your waste factor.
Should I order 12-foot or 15-foot carpet?
Order 12-foot goods for most rooms — it is the standard width and easiest to handle. Order 15-foot goods for rooms wider than 12 feet to avoid a seam down the middle, or when the supplier’s pattern is only available in 15-foot width. The calculator assumes 12-foot goods; for 15-foot, divide the total square footage by 15 to get the linear feet.
Does this calculator include carpet pad?
No — this calculator estimates the carpet only. Carpet pad (cushion) is sold separately by the square yard and usually matches the carpet square-yardage, so order the same number of square yards of pad. Ask your supplier whether pad is included in the per-yard price.
How this calculator works
Net area = length × width.
Total sq ft to order = net area × waste factor.
Square yards = total sq ft ÷ 9 (one square yard = 9 sq ft).
Linear feet of 12-ft roll = total sq ft ÷ 12, rounded up.
Tips for accurate estimates
Use 10% waste for a straight lay in a rectangular room, 15% for rooms with closets or many angles, and 20% for patterned carpet that must be matched across seams.
Carpet is priced and ordered by the square yard, but rolls come 12 or 15 feet wide — check your supplier’s roll width and adjust the linear-foot estimate if you order 15-ft goods.
Always round the linear-foot count up to a whole foot and order a little extra for seaming and future repairs; matching dye lots later can be difficult.
Frequently asked questions
How do I calculate how much carpet I need?
Multiply the room length by the width to get the net square footage, apply a waste factor (10% is standard), then divide by 9 to convert to square yards — the unit carpet is sold by. This calculator does that automatically and also estimates the linear feet of 12-foot-wide roll.
How many square feet are in a square yard of carpet?
One square yard equals 9 square feet (3 ft × 3 ft). To convert square feet to square yards, divide by 9. For example, 135 sq ft of carpet equals 15 square yards.
What waste factor should I use for carpet?
Use 10% for a straight lay in a rectangular room, 15% for rooms with closets or many angles, and 20% for patterned carpet that must be matched across seams. The waste factor covers cuts, seaming, and pattern repeat.
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Related checklist
Pair this estimate with a trade-specific inspection checklist for a clean, verified close-out: Flooring punch list checklist.