Carpet Calculator
Square yards of carpet for a room, with waste for seams and trim.
Input sheet
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Carpet is priced by the square yard and cut from 12 ft-wide rolls, which means the roll geometry — not just the room's area — decides how much you buy. This calculator converts room size to square yards with a waste allowance for seams and trim.
How it works
Room area plus waste, divided by 9 for square yards (how carpet is priced). Carpet comes on 12 ft rolls, so wider rooms get seamed.
The base math is room area in square feet, plus waste, divided by 9 to reach square yards. Waste covers the trim at walls and the extra length a seam layout consumes; 10% suits most rooms.
The 12 ft roll is the catch. A room up to 12 ft wide carpets seamlessly with a single length of roll. Wider rooms need a seamed fill strip, and patterned carpet must also match at that seam — which is why patterned goods get a 15% allowance instead.
Square yards = room length × width × (1 + waste) ÷ 9, rounded up. Standard roll width is 12 ft.
Worked examples
A 14 × 12 ft bedroom with 10% waste. → 21 square yards.
168 sq ft × 1.1 = 184.8; ÷ 9 = 20.5, rounded up to 21 sq yd. The 12 ft width fits the roll with no seam.
A 20 × 14 ft living room with 10% waste. → 35 square yards, with one seam.
280 × 1.1 = 308; ÷ 9 = 34.2 → 35 sq yd. At 14 ft wide, a 2 ft seamed strip fills past the roll's 12 ft.
Tips & gotchas
- Plan seams to run away from windows and under furniture — light raking across a seam is what makes it visible.
- Buy pad by the same yardage; a dense 8 lb pad extends carpet life more than a carpet upgrade at the same total cost.
- For patterned carpet, give the installer the pattern repeat before ordering — matching can add a full pattern length per seam.
FAQ
Does the pad count too?
Yes — figure the same square yardage of pad. A quality pad extends carpet life more than upgrading the carpet itself.
How do square feet convert to square yards?
Divide by 9 — a square yard is 3 × 3 ft. A 180 sq ft room is 20 sq yd before waste.
Can stairs use this calculator?
Estimate each step as roughly 18 in of carpet length (tread plus riser) at the stair's width, then add it to the room total with the same waste.
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