How to use the carpet calculator
- Enter the Room length (ft) and Room width (ft) at the longest and widest points, measuring to the middle of any doorway.
- Pick the Carpet roll width. A 12 ft roll is the most common, and 13 ft 6 in and 15 ft are the other choices.
- Leave Trim allowance per edge (in) at 3, or change it. It is the extra carpet trimmed off at each wall. Enter 0 for an exact fit.
- Fill in Carpet price per sq yd ($), Padding per sq yd ($) and Installation per sq yd ($), or set any of them to 0.
- Read the square yards to order, the seams and the costs. The roll comparison shows how each width changes the order.
How the order is worked out
Carpet comes on a roll of fixed width, so you pay for the full width even when the room is narrower. The calculator lays strips along one side of the room. The other side, plus the trim allowance on both edges, decides how many strips you need, and more than one strip means a seam. Each strip is the room length plus the trim allowance. It tries both directions and keeps the one that uses less carpet. The order is strips x roll width x strip length, divided by 9 for square yards. Flooring Clarity gives 12 ft and 15 ft as the usual roll widths and 9 sq ft per sq yd.
Worked example with the default inputs
A 12 x 10 ft room is 120 sq ft, or 13.33 sq yd. On a 12 ft roll with 3 in of trim per edge, the 10 ft side plus 0.5 ft is 10.5 ft, which fits across the roll. The strip runs along the 12 ft side and is 12.5 ft long, so the order is 12 x 12.5 = 150 sq ft, or 16.67 sq yd, with no seams and 30 sq ft (25%) beyond the room. Carpet at $35 is $583.33. Padding at $5 and installation at $7 use the 13.33 sq yd floor area, which is $66.67 and $93.33. The total is $743.33.
Limits and edge cases
- Patterned carpet and directional pile need extra length to match across seams. Flooring Clarity suggests 10% to 15% more, so add it to the order.
- Closets, stairs and odd-shaped rooms are not handled. Run each as its own rectangle and add the results. This Old House advises adding 10% to the total area as a margin.
- Installers differ on how they bill. This estimate bills carpet on the amount ordered and padding and installation on the floor area, so confirm how your quote is measured.
- Convert units with the area converter. To compare floors, try the tile calculator, and find an area with the rectangle area calculator.
Frequently asked questions
How many square yards of carpet do I need for a 12 x 12 room?
The room is 144 sq ft, or 16 sq yd. With 3 inches of trim per edge, a 13 ft 6 in roll needs 18.75 sq yd and a 15 ft roll needs 20.83 sq yd. A 12 ft roll is no wider than the room, so it needs two strips and a seam, which is 33.33 sq yd.
How do I convert square feet to square yards for carpet?
Divide square feet by 9, because a square yard is 3 ft by 3 ft. A 120 sq ft room is 13.33 sq yd. To turn a price per square yard into a price per square foot, divide it by 9.
Can a wider roll avoid a seam?
Often. When one side of the room plus trim is wider than 12 ft, a 13 ft 6 in or 15 ft roll can cover it in one piece. Check the roll comparison, because the wider roll is not always cheaper.
Sources: Flooring Clarity, How to Measure for a Carpet Accurately; This Old House, How To Measure for Carpet Replacement.