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Carpet Calculator: How Much Carpet Do You Actually Buy?

Carpet comes in fixed-width rolls, so you usually buy more than your floor area. See how much, in square feet and yards, and how room direction changes it.

Updated
Reading time2 min
Sources verified

Key takeaways

  • Carpet comes off a roll, so what you buy can be well above your floor area.
  • Running the roll the other way can change the amount, so check both.
  • Old flooring under carpet can contain asbestos, so check before you remove it.

Enter your room's size and the carpet's roll width. The tool runs the roll both ways across the room and shows the option that buys less.

  • Carpet to buy360 sq ft40 square yards, against 270 sq ft of floor
  • Layout2 lanes of 15 ft1 seam. Ask where they'd fall, as seams can decide the direction.

Nothing you enter leaves your browser. A planning figure for one rectangular room. An installer's seam plan and pile direction can change the amount.

Show the math with your numbers
  1. Floor: 18 × 15 = 270 sq ft
  2. Lanes: 2 of 12 ft, each 15 ft long
  3. To buy: 30 × 12 × 1 = 360 sq ft
What if: roll width
Roll widthCarpet to buy
12 ft (yours)360 sq ft
13.5 ft405 sq ft
15 ft270 sq ft

How the calculator works

  1. Lanes: room width ÷ roll width, rounded up
  2. Linear feet: lanes × room length
  3. To buy: linear feet × roll width × (1 + extra %)
  4. Then it repeats this with the room turned 90° and keeps the smaller answer.

This is our own geometry for a single rectangular room. An installer's layout can differ, so it's a planning figure.

Worked example

An 18 × 15 foot room with a 12-foot roll:

Direction Lanes Linear feet Carpet to buy
Running along the 18 ft side 2 36 432 sq ft
Running along the 15 ft side 2 30 360 sq ft

So you'd buy 360 square feet, or 40 square yards, for a floor of 270 square feet. Some of that surplus can fill closets or doorways, so ask your installer.

Roll width changes the result

For the same room:

Roll width Layout To buy
12 ft 2 lanes of 15 ft 360 sq ft
13.5 ft 2 lanes of 15 ft 405 sq ft
15 ft 1 lane of 18 ft 270 sq ft

A wider roll can remove the seam and the surplus here, so ask which widths your carpet comes in.

The cheapest layout isn't always best

Ask your installer about:

  • Seams: where they'd fall, particularly in doorways, walkways and across the light from windows
  • Pile direction: lanes usually need to run the same way, which can limit how offcuts are used
  • Patterns: these need matching, which adds carpet

Your quote

Carpet is often priced by the square foot or yard, and that may or may not include pad, removal and installation. Ask for the measured area, and compare it with the figure here.

Before you pull it up

Old vinyl tile, sheet flooring and adhesive under carpet can contain asbestos. EPA says not to sand, scrape or power-strip it. Read about old flooring before you go further.

Frequently asked questions

How much carpet do I need for a 12 × 12 room?

On a 12-foot roll, one 12-foot lane, or 144 square feet, which is 16 square yards. Check for doorways and closets.

How do I convert square feet to square yards?

Divide by 9.

Why does the quote exceed my floor area?

Carpet comes in fixed widths, so you often buy offcuts along with the room. Ask to see the layout.

Sources

We use primary sources where we can: building codes, federal rules and manufacturer documents. Read our editorial standards.