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Sofa Size Calculator

Find the ideal sofa length for your wall with comfortable clearance on both sides.

How it is calculated

The tool leaves a gap at both ends of the wall and gives the rest to the sofa: sofa length = wall − 2 × clearance. Both values are in centimetres. If the clearance box is empty, or negative, the tool uses 45 cm per side. A clearance of 0 is accepted and gives a sofa as long as the wall. The seat count is floor(sofa length ÷ 60), based on about 60 cm per seat and rounded down to whole seats. The wall width must be above zero, and the clearance on both sides together must leave a positive length, otherwise there is no result. The depth of the sofa, armrest width and doorways are not considered, so treat the answer as the longest sofa that fits, not as an exact product size.

Worked example

A wall 360 cm wide, with 30 cm kept free on each side for a side table or lamp. Total clearance: 2 × 30 = 60 cm. Sofa length: 360 − 60 = 300 cm. Seats: 300 ÷ 60 = 5, so about 5 seats. If you leave the clearance blank, the default of 45 cm per side applies instead: 360 − 90 = 270 cm and 4 seats (270 ÷ 60 = 4.5, rounded down).

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Common mistakes

  • Entering the wall in metres or inches. Both fields are in centimetres, so a 3.6 m wall must be typed as 360.
  • Thinking the clearance is the total gap. It is subtracted once per side, so 30 means 60 cm taken from the wall.
  • Leaving the clearance blank and not noticing the 45 cm default per side, which shortens the sofa by 90 cm in total.
  • Treating the seat count as exact. Seats are counted at 60 cm each and rounded down, but real sofas have arms that eat into the width.
  • Measuring the wall at the skirting board only. A radiator, window sill or door swing can reduce the usable width.

About this calculator

This calculator recommends a sofa length by taking the wall width and subtracting clearance on each side — 45 cm (about 18 inches) per side unless you enter your own, the space interior designers leave for walking room, end tables, or a floor lamp beside the sofa. Pushing a sofa edge-to-edge across a wall is a common furnishing mistake that leaves no breathing room in the layout and makes the piece look oversized relative to the room.

Interior designers and furniture shoppers use this before buying to avoid the two most common sizing errors: a sofa that overwhelms a wall with no clearance, or one so undersized it leaves an awkward gap, both of which are easy to spot in a showroom's open floor but hard to judge from a tape measure alone.

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  • Editorial team

    Run it twice to get a shopping range: once with the default 45 cm per side for a freestanding sofa, and once with 0 for an alcove or a built-in look where the sofa meets both walls. Seats are counted at 60 cm each and rounded down, so 4.5 shows as 4. Does one side of your wall need extra room, say for a radiator or a door swing? Tell us if separate left and right gaps would help.

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