Carpet is one of the few floor coverings still commonly priced by the square yard in the US, while rooms are usually measured in feet. That mismatch is where mistakes creep in. This carpet calculator takes your room measurements in feet and inches (or metres), converts them to square yards, adds an allowance for seams and trimming, and multiplies by the price per square yard to give you a budget.
How to use the carpet calculator
- Measure each room at its longest and widest points, wall to wall, including closets the carpet will go into.
- Enter the measurements and choose the shape. Add each room with Add to total if you are carpeting several.
- Set the waste allowance. 10% is a sensible starting point; see below for when to use more.
- Enter the price per square yard from your quote, ideally including pad and installation, to see the total.
Why carpet needs extra
Unlike tiles or planks, carpet comes off a roll of fixed width. In the US most broadloom carpet is 12 ft wide, with some styles made in 15 ft widths; European rolls are often 4 m or 5 m wide. Every room is cut from that roll, so the amount you buy depends on how the room’s width fits the roll, where the seams go, and the direction of the pile. Pile must run the same way in every piece, or seams show as a change in shade, so off-cuts can’t always be turned to fill a gap.
- Rooms up to 12 ft wide can usually be covered with one piece, so waste is just the trim around the edges.
- Rooms wider than the roll need a seam and a fill strip, which often adds 10–20%.
- Patterned carpet must be matched at seams, which adds more again.
Your installer will draw a seam plan to get the exact order, but the calculator gets you a reliable estimate before you ask for quotes.
Worked example
A bedroom measures 11 ft 6 in × 15 ft.
- Floor area: 11.5 × 15 = 172.5 sq ft = 19.17 sq yd.
- The room is narrower than a 12 ft roll, so it can be cut as one 12 × 15 ft piece: 180 sq ft = 20 sq yd purchased, about 4.3% extra.
- At $32 per square yard including pad and installation: 20 × 32 = $640.
Carpet needed for common room sizes
| Room size | Square feet | Square yards | Typical use |
|---|---|---|---|
| 10 × 10 ft | 100 | 11.11 | Small bedroom, home office |
| 10 × 12 ft | 120 | 13.33 | Bedroom, nursery |
| 11 × 12 ft | 132 | 14.67 | Bedroom |
| 12 × 12 ft | 144 | 16 | Bedroom, dining room |
| 12 × 14 ft | 168 | 18.67 | Large bedroom, kitchen |
| 12 × 15 ft | 180 | 20 | Living room, primary bedroom |
| 12 × 16 ft | 192 | 21.33 | Family room, primary bedroom |
| 13 × 15 ft | 195 | 21.67 | Primary bedroom |
| 14 × 16 ft | 224 | 24.89 | Living room |
| 15 × 20 ft | 300 | 33.33 | Large living room |
| 16 × 20 ft | 320 | 35.56 | Great room, open-plan kitchen |
| 20 × 20 ft | 400 | 44.44 | Two-car garage |
Carpet pad and stairs
Pad (underlay) goes under the carpet and is usually priced per square yard or per square foot. It is laid in strips without matching pile, so you need roughly the room’s floor area plus a small allowance, rather than the full carpet order.
Stairs are measured step by step. For each step, add the tread depth, the riser height and the bit that wraps around the nosing, then multiply by the width of the stair. Add the steps together and include any landing as a separate rectangle. Installers often charge stairs per step, so ask how your quote is priced.
Tips for a smooth carpet order
- Measure into doorways to the middle of the door when it is closed, so the carpet meets the next floor neatly.
- Ask whether your quote includes pad, installation, removal of old flooring, moving furniture and transition strips.
- Compare quotes on the same basis: price per square yard installed, for the same number of square yards.
- Order all the carpet for connected rooms together so it comes from the same production run.
Frequently asked questions
How much carpet do I need for a 12×12 room?
A 12 × 12 ft room is 144 sq ft, or 16 square yards. Because it fits exactly on a 12 ft roll, little extra is needed; plan for around 16 to 17.6 sq yd with a small trimming allowance.
How do I convert square feet to square yards for carpet?
Divide the square feet by 9. For example, 270 sq ft ÷ 9 = 30 square yards.
How much extra carpet should I buy?
Around 10% is typical, rising to 15–20% for rooms wider than the roll, rooms with many angles, and patterned carpet that must be matched at seams.
What width does carpet come in?
In the US, most broadloom carpet comes in 12 ft rolls, and some styles in 15 ft. European carpet is usually 4 m or 5 m wide.
Is carpet priced per square foot or per square yard?
Both are used. Many US stores advertise per square foot but installers often quote per square yard. Divide a per-square-yard price by 9 to compare it with a per-square-foot price.
Do I need to buy pad for the same area?
Pad is needed for the floor area being carpeted, but it doesn’t need extra for pile direction or seams, so you usually need slightly less pad than carpet.
How do I measure stairs for carpet?
For each step, add the tread depth, riser height and nosing wrap, multiply by the stair width, then add up all the steps and any landings.