Why is carpet sold by the square yard?

Because it comes off a roll of fixed width, and the shop sells you running length of that roll. A square yard is nine square feet, so the price per square foot is a ninth of the quoted figure — comparing a per-yard price against a per-foot one makes carpet look nine times dearer than laminate when it is not.

How wide does carpet come?

Twelve feet, almost always, in the US. Thirteen feet two inches appears where the mill is metric — that is four metres — and fifteen feet exists but is hard to get. Any room wider than the roll needs a seam, and where that seam falls is worth deciding before ordering.

Why did the calculator charge me for so much waste?

Because a 14 ft room off a 12 ft roll takes two strips and throws most of the second away. Running the strips the other way — along the 14 ft dimension rather than the 18 ft one — often turns two long strips into two short ones. Try both ways round in the fields above.

Do I need to add for a pattern?

Yes, one full repeat per seam. A carpet with a 12 in repeat costs an extra foot of length on every strip after the first, because the pattern has to line up across the join. That is what the upper end of the waste allowance is for.

Carpet Calculator

With room length 18 ft, room width 14 ft, pattern and trim waste 10 %, carpet comes to 52.8 sq yd — square yards to buy. It is reached in 6 steps, the last of which is 475.2 / 9, and each one is printed on the page with its numbers filled in. The formula is the one published by Carpet and Rug Institute, not an approximation fitted to it.

Square yards of carpet from a 12 ft roll, with the seam waste a room wider than the roll actually costs.

Formula and sources checked 16 August 2026 · How we check

Room length 18 ft, Room width 14 ft, Roll width 12 ft — the usual width, Pattern and trim waste 10

52.8 sq yd

Square yards to buy for the example below. Editing a field recomputes the calculator below; this figure holds the answer the page was loaded with.

It is written into the HTML rather than drawn by a script, so a search engine reading this page without running JavaScript still finds an answer.

Room lengthRoom widthRoll widthPattern and trim waste%10% plain, up to 20% for a pattern that has to match across a seam.

Square yards to buy

52.8 sq yd

Floor area: 18 * 14252 sq ft
Strips off the roll: ceil(14 / 12)2 strips
Length of roll to buy: 2 * 18 * (1 + 10 / 100)39.6 ft
Carpet bought: 39.6 * 12475.2 sq ft
Square yards: 475.2 / 952.8 sq yd
Paid for and not laid: 475.2 - 252223.2 sq ft

Several at once

A job is rarely one of anything. Work out the first, add it, change the figures and add the next — the list keeps what each line was, and totals them.

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Worked example

An 18 × 14 ft room is 252 sq ft, but a 14 ft width does not come off a 12 ft roll in one piece. Two strips of 18 ft plus 10% is 39.6 running feet, which is 475 sq ft or 52.8 sq yd — 223 sq ft paid for and not laid. Turning the layout so the strips run the other way costs less.

How to work it out yourself

1.Measure the room at its widest points, including doorways and alcoves.
2.Divide the room width by the roll width and round up — that is the number of strips, and two strips means a seam.
3.Multiply strips by room length, add 10% plain or up to 20% for a pattern repeat.
4.Multiply the running feet by the roll width for square feet, then divide by 9 — carpet is priced by the square yard.

The formula

Floor area18 * 14
Strips off the rollceil(14 / 12)
Length of roll to buy2 * 18 * (1 + 10 / 100)
Carpet bought39.6 * 12
Square yards475.2 / 9
Paid for and not laid475.2 - 252

Source: Carpet and Rug Institute, ASTM D5252 — carpet installation practices

Questions people actually ask

Why is carpet sold by the square yard?: Because it comes off a roll of fixed width, and the shop sells you running length of that roll. A square yard is nine square feet, so the price per square foot is a ninth of the quoted figure — comparing a per-yard price against a per-foot one makes carpet look nine times dearer than laminate when it is not.
How wide does carpet come?: Twelve feet, almost always, in the US. Thirteen feet two inches appears where the mill is metric — that is four metres — and fifteen feet exists but is hard to get. Any room wider than the roll needs a seam, and where that seam falls is worth deciding before ordering.
Why did the calculator charge me for so much waste?: Because a 14 ft room off a 12 ft roll takes two strips and throws most of the second away. Running the strips the other way — along the 14 ft dimension rather than the 18 ft one — often turns two long strips into two short ones. Try both ways round in the fields above.
Do I need to add for a pattern?: Yes, one full repeat per seam. A carpet with a 12 in repeat costs an extra foot of length on every strip after the first, because the pattern has to line up across the join. That is what the upper end of the waste allowance is for.

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