ConverterHub

Carpet Calculator

Enter the room dimensions and roll width to get the area, linear metres and waste.

Result

22.88 m²
10.40 m
18.72 m²

How it is calculated

All three inputs are in metres. The strips of carpet run along the room's length, and the roll width is the cut width of each strip. The number of strips is S = ceil(width / roll width), rounded up to a whole strip. Then linear metres = S × length, carpet bought = S × roll width × length in m², floor area = length × width and waste = bought − area, never below zero. Two inputs are treated as fixed: the room is a plain rectangle, and the strips run parallel to the side you called length. The tool does not turn the room around to look for a cheaper layout, nor does it add allowances for pattern matching, seams or fitting.

Worked example

A room 5.2 m long and 4.4 m wide, carpet from a 4 m roll. Floor area = 5.2 × 4.4 = 22.88 m². Strips = ceil(4.4 / 4) = 2. Linear metres = 2 × 5.2 = 10.40 m. Carpet bought = 2 × 4 × 5.2 = 41.6 m². Waste = 41.6 − 22.88 = 18.72 m². Swapping the two sides, so that the strips run along the 4.4 m side, needs only 8.80 m of roll, so it is worth trying both ways.

Try this example →

Common mistakes

  • Entering the length and width in the wrong order. The strips run along the length, so swapping them changes the linear metres. For the same room, 5.2 by 4.4 needs 10.40 m and 4.4 by 5.2 needs 8.80 m.
  • Entering the roll width in feet or the room in centimetres. All three values are in metres, so a 12-foot roll is about 3.66.
  • Buying exactly the linear metres shown and nothing more. The tool adds no allowance for pattern matching, seams, or doorways and alcoves.
  • Reading the waste figure as a cost you must accept. It counts the unused part of the second strip, and an offcut of that size may be usable in a cupboard or hallway.
  • Treating the area as the amount to order. Carpet is sold from a roll of fixed width, so the linear metres is the figure that matters when you buy.

About this calculator

Carpet is manufactured and sold in long rolls of a fixed width (commonly 12 feet or 4 metres), so buying carpet for a rectangular room isn't as simple as multiplying floor area. You need to work out how many linear metres of that fixed-width roll must be cut to fully cover the room, and because a roll's width rarely divides the room's dimensions evenly, some cutting waste is almost always unavoidable.

Installers and homeowners use this kind of calculation to get an accurate materials estimate before ordering, since underestimating carpet means a delayed second order (and possible dye-lot mismatches between batches), while overestimating means paying for material that ends up as offcuts. The waste factor grows with room shapes that don't align neatly with the roll orientation, alcoves, and any pattern that needs to be matched at seams.

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