How to Measure a Room for Carpet

Measure the full width and full length of the room at its widest points, including any doorways, bay windows and alcoves, then add an allowance for trimming. Carpet is sold from a roll in a fixed width, so the usable figure is not the floor area in square metres but the length of roll needed to cover the room in one piece.

That last point is why two rooms of identical square metreage can cost noticeably different amounts.

Why You Measure the Widest Point, Not the Average

A room is almost never a true rectangle. Walls bow, chimney breasts intrude, and doorways need carpet carried into them so the join sits under the door rather than in the room.

If you measure the narrow part of an irregular room and order to that figure, the carpet will not reach. Fitters always work to the widest point in each direction and trim the surplus away, because you can cut carpet down but you cannot stretch it.

How Roll Width Changes the Figure

Carpet and vinyl come on rolls of a set width, most commonly 4 metres, with extra wide 5 metre rolls also available. The calculation is not length times width, it is how much roll length you need at the available roll width.

A room 3.6 metres wide fits comfortably inside a 4 metre roll. A room 4.2 metres wide does not, so it either needs a 5 metre roll or it needs a join. We hold both 4 metre and extra wide 5 metre rolls in stock precisely so that fewer rooms end up needing a seam.

Stairs Are Measured Differently

Stairs are measured per tread and riser, not as a floor area. As a rough guide, allow around 500mm of carpet length for each step to cover the tread and the riser together, then add the landing separately.

A straight flight is predictable. A flight with a winder, which is a turning step at the top or bottom, needs considerably more carpet, because each turning step has to be cut individually and the waste is unavoidable. This is the single most common reason a staircase quote comes back higher than people expect.

Why Fitters Add a Waste Allowance

A professional measure includes an allowance over and above the bare dimensions. This covers trimming, pattern matching where the carpet has a repeat, and the simple fact that a cut edge needs to be squared up.

On a patterned carpet the allowance is larger, because the pattern has to line up across a doorway or a join. Ordering to the exact millimetre with no allowance is how people end up a few centimetres short with no roll left to cut from.

Should You Measure It Yourself?

Measuring your own rooms is useful for getting a rough idea of budget before you start looking, and we would encourage it. We would not recommend ordering from your own measurements.

The risk sits entirely with whoever measured. If a professional measure is wrong, that is the fitter's problem to put right. If your own measure is wrong, the carpet has already been cut from the roll. Our measuring and quoting is free and carries no obligation, so there is little reason to take that risk.

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