Carpet Calculator

Carpet worked out the way it's cut, in strips off a 12 or 15 ft (or 4 or 5 m) roll: length off the roll, square yards or m² to buy, seams and underlay.

Carpet comes off a roll of fixed width, typically 12 ft (some 15 ft) in the US, 4 m or 5 m in the UK and 3.66 m or 4 m in Australia, so what you buy depends on how the room's sides fit the roll, not just its area. A 15 × 13 ft room is 195 ft², but from a 12 ft roll it needs two strips: two 13.5 ft lengths, 27 ft off the roll, which is 324 ft² or 36 square yards. From a 15 ft roll the same room fits in one strip: 13.5 ft off the roll, 22.5 square yards. This calculator lays out each room both ways and picks the one that uses less carpet, showing the length off the roll, the square yards or m² to buy, the seams, and the underlay and gripper needed.

Units
Bag sizes
Room
ft
ft
Feet and inches work too: type 12'6 or 12.5.
in
Off the roll
27 ft

12 ft wide

To buy
36 yd²

324 ft²

Underlay
195 ft²

gripper or tack strip 56 ft

Seams
1

195 ft² of floor

How it was worked out
  1. Room: 15 × 13 ft; strips run along the width: 2 strips of 13.5 ft = 27 ft off the roll, 1 seam
  2. 27 ft × 12 ft roll = 324 ft² (36 yd²)

Each room is worked out on its own, with all strips laid the same way so the pile matches. A fitter may use offcuts across rooms or in closets, so their figure can be a little lower.

Common use cases

  • Order carpet for a bedroom, stairs landing or living room
  • See whether a wider roll saves money for your room
  • Check a carpet shop's quote in square yards or m²
  • Work out underlay and gripper or tack strip at the same time

How to use

  1. Choose your units and country (for the usual roll widths).
  2. Enter each room's length and width.
  3. Pick the roll width and keep or change the trim allowance per strip.
  4. Read the length off the roll, the area to buy and the seams.

FAQ

How do I calculate how much carpet I need?

Work out how many roll widths cover the room's width, then multiply by the room's length plus a little for trimming; that's the length off the roll. Multiply by the roll width for the area you pay for. Try both directions and use the smaller.

How many square feet are in a square yard?

9. US carpet is often priced per square yard, so divide the square feet by 9. A square yard is about 0.84 m².

Why do carpet shops sometimes quote a little less?

A fitter may use offcuts in closets, landings or other rooms, as long as the pile runs the same way. This calculator works out each room on its own, so it's a safe upper figure.

Related tools