Carpet Calculator

Why carpet is sold by the square yard

Flooring is the one place where American retail still works in yards. Carpet is priced and ordered per square yard, which is a 3 ft by 3 ft square, or 9 square feet. That single conversion is the source of most of the confusion, because everyone measures rooms in feet and buys carpet in yards.

So the first job is always the same: multiply length by width in feet, add up every room, then divide by 9. A 12 x 15 room is 180 sq ft, which is 180 ÷ 9 = 20 square yards. A 10 x 12 room is 120 sq ft, or 13.3 square yards. It is not complicated, but it is easy to get wrong at the end of a long day.

The second job is the one people forget. Carpet does not arrive as a magic shape that fits your room. It arrives as a roll, almost always 12 feet wide, and the installer cuts pieces out of it. If your room is wider than 12 feet, they have to run two pieces side by side and seam them. That changes both the amount you need and the price, which is why a pure square-footage estimate can come up short.

Worked example: a 12 x 15 bedroom

Start with the simplest case: one bedroom, 12 ft by 15 ft, one plain carpet, 10% waste allowance.

• Area: 12 × 15 = 180 sq ft
• Square yards: 180 ÷ 9 = 20 sq yd
• With 10% waste: 20 × 1.10 = 22 sq yd

Now the roll math. The room is 12 ft wide and the roll is 12 ft wide, so it fits in one piece with no seam. The installer needs one strip 12 ft wide by 15 ft long, so 15 linear feet off the roll. That strip contains 15 × 12 = 180 sq ft of carpet, which is exactly the room, plus whatever the cut-offs give you.

Add a second room, 10 x 12 (120 sq ft), and the totals become 300 sq ft, 33.3 sq yd, and 36.7 sq yd with waste. At $3.00 per square yard for the carpet and $0.60 per square yard for 8-pound padding, that is 36.7 × $3.00 = $110 in carpet and 33.3 × $0.60 = $20 in padding, before installation. Installation at $2.00 per square yard on 33.3 sq yd adds another $67, so the whole job lands near $197 in materials and labor for 300 sq ft.

Waste, seams and roll width

Waste is not padding for the installer, it is the reality of cutting rectangles out of a roll to fit an irregular room. Here is how much to allow.

Roll width is the other lever. A 12 ft roll covers any room up to 12 ft wide in a single piece. A 15 ft roll covers rooms up to 15 ft wide, which is why 14 x 16 master bedrooms often use 15-foot goods. If your room is 13 ft wide and you only have a 12 ft roll, the installer runs two 12-foot strips and seams them down the middle, you pay for two full strips even though the second one is only 1 ft of actual carpet. For a 13 x 20 room, that is two strips of 20 linear feet, or 40 linear feet of roll, instead of the 20 feet a 15-foot roll would have used. Always check the roll width before you commit.

The Carpet and Rug Institute publishes guidance on installation and seam placement that is worth a look if you are deciding between a 12 and a 15 foot roll.

Padding, stairs and closets

Carpet needs padding under it, and padding is priced and sold the same way, by the square yard. As a rule, order the same square yardage as the carpet. Padding is easier to piece than carpet, so you can often get away with 5% less, but ordering the same amount keeps it simple and the leftovers are useful for stairs.

Stairs are the item that blows up budgets. A standard stair tread is 36 inches wide and 10 inches deep, and the installer has to wrap the carpet over the nose and down the riser. In practice a stair takes about 3 to 4 linear feet of 12-foot carpet per step. Thirteen steps therefore need 39 to 52 linear feet off the roll, which at 12 feet wide is 39 × 12 = 468 sq ft to 52 × 12 = 624 sq ft, or 52 to 69 square yards of roll for what is only about 60 square feet of visible surface. Stairs are the least efficient carpet job in a house.

Closets count fully. A walk-in closet with a 2 ft deep return uses extra carpet because the installer has to run the goods into the opening and trim. Add the closet floor area plus 5 sq ft per closet for the returns, and remember that closet carpet is usually cut from the same roll, so it does not add to your square-yard order, it just consumes waste.

Estimating cost before you shop

Prices vary widely, so the point of an estimate is to know the shape of the bill before a salesperson gives you a number.

400 sq ft is 44.4 square yards, so a mid-grade nylon job with padding and labor comes to roughly 44.4 × ($3.00 + $0.60 + $2.00) = $249, plus a tear-out charge of $0.50 to $1.00 per square yard if there is old carpet to remove and haul away.

Two things drive the final bill more than the carpet itself: stairs, which are priced per step at $5 to $15 each, and furniture moving, which some installers charge for. Get a written quote that lists square yards, padding, labor, tear-out and stairs as separate lines. Shaw's measuring guide walks through the same steps if you want a second opinion on your numbers.

Measuring your rooms the right way

Measure at the widest point of each room, not the middle. If a wall bows or a doorway juts out, use the larger dimension, because the installer cuts to fit the largest span.

• Measure length and width in feet and inches, then convert to decimal feet. A room 12 ft 6 in wide is 12.5 ft.
• Add up every room that uses the same carpet, then divide the total square feet by 9.
• Sketch the layout and mark which walls have doorways, because the installer needs to know where seams can go.
• Note any room wider than 12 feet, it changes the roll math entirely.

If you are working in meters, convert once at the start rather than mixing units. Our meters-to-feet converter and the inches-to-cm converter both handle that in one step, and keeping everything in feet until the final division by 9 avoids the most common mistake.

Finally, this is an estimate, not a cutting list. A professional installer measures on site and will adjust for doorways, subfloor condition, pattern repeats and stair layout. Use the numbers here to budget and to sanity-check a quote, and confirm the final order with your installer before you buy.