ToolwickCarpet Calculator (Square Yards)
Use this free carpet calculator to find how many square yards of carpet you need for a room. Enter the length and width, choose a roll width and waste allowance, and get a rounded-up order quantity plus carpet pad and tack strip estimates.
Enter your room size and press Calculate to see your roll layout.
How to Use This Carpet Calculator
Pick feet or metres, then enter the room's length and width at the longest points. Set the waste slider, choose the roll width your supplier stocks, and add stair steps or a price per square yard if you want them included. Press Calculate to see the recommended order in square yards, a roll-width comparison, and the pad and tack strip you will need. For L-shaped rooms, run the calculator once per rectangle and add the totals.
Why This Matters
Carpet is sold by the square yard, but rooms are measured in square feet, and that mismatch causes more ordering mistakes than almost anything else in flooring. A 12 × 15 ft bedroom is 180 square feet, which is 20 square yards, yet shoppers often order 180 or guess based on a neighbour's room. Order too little and you may not be able to match the dye lot later, which means a visible seam or a full re-order. Order too much and at $20–$45 per square yard, three spare yards is $60–$135 wasted.
Broadloom also comes in fixed widths, usually 12 ft. A room that is 12 ft 3 in wide needs two strips and a seam, even though it is only three inches over, so the roll layout often matters more than the raw area. This matters to homeowners getting quotes, landlords re-carpeting rentals between tenants, and DIYers who plan to lay carpet tiles or roll goods themselves. Knowing your number before you walk into the store lets you check an installer's quote and compare roll widths on price.
How It's Calculated
The calculator runs two estimates and recommends the larger one, so the answer never errs on the short side.
Area-based sq yd = Area × (1 + waste %) ÷ 9
Strips = ⌈ room dimension ÷ roll width ⌉
Linear ft = strips × (strip length + 0.25 ft trim)
Roll-based sq yd = Linear ft × roll width ÷ 9
Order = larger of the two, rounded up to 0.1 sq yd
The tool tests running strips along the length and along the width, and uses whichever needs less roll. Pad is room area plus 5%, rounded up. Tack strip is the room perimeter, rounded up to whole 4-ft lengths, with no deduction for doorways.
These are common installer rules of thumb (9 sq ft per square yard, a 3-inch trim allowance, 5–15% waste), not a building code. Carpet quantity is not a code-sized item, but local rules on stair coverings or fire ratings may apply, so confirm with your installer. Pattern repeats, nap direction and unusual layouts can raise the real number. Treat the result as a planning estimate, not an installation quote or approval.
Worked Example
A living room measures 15 ft × 12 ft, with 10% waste, a 12 ft roll, no stairs and carpet at $24 per square yard.
- Room area: 15 × 12 = 180 sq ft.
- Waste: 180 × 1.10 = 198 sq ft ÷ 9 = 22.0 sq yd (area-based).
- Roll layout along the 15 ft length: ⌈12 ÷ 12⌉ = 1 strip, 15 + 0.25 = 15.25 linear ft × 12 ÷ 9 = 20.33 sq yd. Running across the width needs 2 strips and 24.5 linear ft, so the first layout wins.
- Recommended order: the larger figure, 22.0 sq yd (198 sq ft). Cost: 22.0 × $24 = $528.00.
- Pad: 180 × 1.05 = 189 sq ft = 21.0 sq yd. Tack strip: perimeter 54 ft ÷ 4 = 13.5, so 14 lengths.
Tips & Common Mistakes
- Measure the longest points. Include closets, alcoves and the area under door swings, not just the main rectangle.
- Don't round down. Carpet is cut from a continuous roll, so a few inches short can mean a seam or a second dye lot.
- Add extra for patterns. Large repeats, diagonal installs and directional pile can need 10–15% waste.
- Keep seams out of traffic. Ask the installer to place seams away from doorways and hallways, even if it costs a little more roll.
- Buy once, from one lot. Keep an offcut after installation for future repairs.
- Confirm on site. Have the installer verify measurements before cutting.
Frequently Asked Questions
How do I convert square feet to square yards for carpet?
Divide the square feet by 9, because a square yard is 3 ft × 3 ft. A 180 sq ft room is 20 square yards before waste. Always add your waste allowance after converting, not before.
How much carpet do I need for a 12 × 12 room?
The room is 144 sq ft, or 16 square yards. With 10% waste you need about 17.6 sq yd. On a 12 ft roll the room needs one strip of about 12.25 ft, so the area-with-waste figure is the one to order.
How much extra carpet should I buy?
Most installers suggest 5–10% for simple rooms and 10–15% for patterned carpet, stairs, or rooms with many corners. If you are unsure, use the higher figure, since running short is the costlier mistake.
What is the standard carpet roll width?
In North America, 12 ft is by far the most common, with 15 ft available for some products. Imported carpet is often 4 m (13 ft 2 in). Wider rolls can avoid seams in larger rooms, so compare them in the table above.
Do I need to buy carpet pad separately?
Usually yes, unless the carpet has an attached backing cushion. Pad is sold by the square yard like carpet, and the calculator adds 5% for trimming. Tack strip is bought separately by the linear foot.
How much carpet do I need for stairs?
Plan on roughly 5 sq ft per step for a standard 36-inch-wide stair with a tread and riser, and more for waterfall or bullnose styles. Stairs are cut into many small pieces, so keep the waste allowance at 10% or higher.