How much carpet do I need?

Priced by the yard, cut by the roll

Carpet is quoted in square yards but it comes off a roll of fixed width, almost always 12 feet, sometimes 15. That mismatch is the whole difficulty. Your room might be 180 square feet, which is 20 square yards, but what you actually buy is a length cut off a 12 foot wide roll — and if the room is wider than the roll, you need more than one strip.

A room narrower than the roll width is the easy case: one strip, cut to the room length, and the leftover along one edge is trim. A room wider than the roll means a seam, and the second strip is rarely used efficiently. That is why the linear figure here can look generous next to the bare area.

Two things a calculator cannot decide for you. Pile direction: every strip must run the same way, or the two pieces will look like different colours under the same light. This is the single most common carpet mistake, and it cannot be fixed after the fact. And seam placement: a seam belongs where traffic and sightlines are lowest, never across a doorway.

The figures here do not include underlay, tack strip or the extra few inches most fitters want on every edge for stretching. Take the square yards to price the job and the linear feet to sanity-check a quote, then let the fitter do their own measure before anything is cut.

A worked example: why the roll direction matters

Take an 11 × 15 foot bedroom. It is 165 ft², or 18.3 square yards of floor. With a 12-foot roll running the 15-foot length, one strip covers the 11-foot width with a foot to spare: you buy 15 linear feet of roll, which is 180 ft² or 20 square yards, and there is no seam.

Turn the roll the other way and the 15-foot width needs two strips, each 11 feet long: 22 linear feet, 264 ft², or 29.3 square yards, with a seam down the room. Same room, almost 50% more carpet. When you enter the room in the calculator, put the dimension closest to (but not over) the roll width as the width, then compare it with the dimensions the other way round.

Rooms against a 12-foot roll

Rooms wider than the roll in both directions are where carpet gets expensive. A fitter can often reuse the second strip's offcut in a closet or a neighboring room, which is why a whole-house quote is usually cheaper per yard than room-by-room.

What else goes with the carpet

• Pad (underlay): the same area as the carpet. A thicker pad is not always better; many carpets specify a maximum pad thickness for the warranty.
• Tack strip: around the room perimeter, minus doorways. For the 11 × 15 room, about 50 feet.
• Transitions: one per doorway where carpet meets another floor.
• Stairs: each step takes roughly a strip 27 to 30 inches long by the stair width. Ask the fitter; stairs are usually priced per step.

Mistakes that cost money

• Mixing pile directions. All strips must run the same way, including closets cut from offcuts.
• Measuring to the baseboard instead of under the door. Carpet runs to the middle of the door threshold. Add those few inches in every doorway.
• Comparing quotes that are not like for like. One quote may include pad, removal of the old carpet and stairs; another may not. Compare the total.

What it costs

Carpet commonly costs about $20 to $60 per square yard in the US for the material, plus pad and installation. For the 20 yd² bedroom, that is roughly $400 to $1,200 in carpet alone. Prices vary widely by fiber and quality.