How to Measure Stairs for Carpet (Step-by-Step)

Measure one step properly, then check three more

The run of carpet over a single step is the tread depth plus the riser height plus the nosing overhang. On a typical staircase that is 250mm + 190mm + 25mm, or 465mm — call it 18.5in in imperial. Take it with a tape laid flat against the timber, following the path the carpet will take rather than measuring in the air, and do it at the middle of the step where the tape sits naturally.

Then measure three more steps, spread through the flight. Houses settle, carpenters improvise, and it is entirely normal for the bottom riser to be 10mm different from the rest because of a floor build-up. If the steps vary, use the largest figure for every step rather than the average: excess carpet is trimmed, missing carpet is a new order.

Full carpet versus a runner

For fully carpeted stairs, use the wall-to-wall width. For a runner, use the runner width and remember you are only covering the middle, which is why a runner uses roughly 60 to 75 per cent of the material a full carpet does. The per-step run is identical either way; only the width changes. If a runner is what you are pricing, the stair runner calculator on the home page gives you the total length and the per-step breakdown in one go.

Winders, landings and the bottom step

Winders are measured individually. Each wedge-shaped tread gets its own carpet piece cut to the widest point of the wedge, so measure the long edge and the depth, then treat it as a rectangle at those dimensions. It wastes material, and there is no way around it. Landings are measured as a plain rectangle, length by width, and added to the total. A bullnose or curtail bottom step needs its own piece measured around the full curved face, typically adding 200mm to 300mm over a plain step.

1. Measure tread depth, riser height and nosing on four different steps.
2. Take the largest of each and add them for the run per step.
3. Count the steps, remembering the top step is often the landing edge.
4. Multiply run per step by step count by carpet width for the area.
5. Measure each winder and each landing separately and add them.
6. Add 10 per cent waste on a plain carpet, 15 to 20 per cent on a pattern or with winders.
7. Convert to the unit your supplier sells in and round up to the next half unit.

Converting to what your supplier sells

Broadloom carpet comes off a 12ft or 15ft wide roll and is sold by the linear metre or linear yard. One linear yard of 12ft broadloom is four square yards; one linear metre of a 4m roll is four square metres. Divide your area by the roll width to get the length to order — but check whether the stair width plus waste actually fits across the roll efficiently, because a 900mm stair cut from a 4m roll leaves a lot of unusable strip unless the fitter can plan several pieces side by side.

Whatever you decide, get the numbers first: the stair runner calculator doubles as a stair runner length calculator, adding nosing wrap, landings, winders, pattern repeat and waste so you order the right length the first time.

Still deciding on material, width or pattern? Our hub on stair runners compares weaves, widths, backings and fitting styles side by side, then hands the numbers straight to the calculator.