Per-step run in millimetres
Carpet does not travel the horizontal distance of a staircase; it travels the surface. Each step contributes the tread depth, the riser height and the nosing overhang. On a UK domestic flight that is 250 + 190 + 25 = 465mm. Measure your own on four separate steps and use the largest figure, because a flight where one step is 10mm deeper will leave you short at exactly the wrong moment.
| Steps | 800mm wide | 900mm wide | 1000mm wide | With 10% waste (900mm) |
|---|---|---|---|---|
| 10 | 3.7 m2 | 4.2 m2 | 4.7 m2 | 4.6 m2 |
| 12 | 4.5 m2 | 5.0 m2 | 5.6 m2 | 5.5 m2 |
| 13 | 4.8 m2 | 5.4 m2 | 6.0 m2 | 6.0 m2 |
| 14 | 5.2 m2 | 5.9 m2 | 6.5 m2 | 6.4 m2 |
| 16 | 6.0 m2 | 6.7 m2 | 7.4 m2 | 7.4 m2 |
Know your numbers in 30 seconds
Enter your step count, tread depth and riser height — the stair runner calculator gives you the exact length to order, in metres and feet, with waste included.
Open the stair runner calculatorAdding landings and winders
A landing is a plain rectangle: length by width, in metres, added straight to the total. A typical 900mm by 900mm half landing is 0.81 square metres. Winders are less forgiving — each wedge is cut to its widest dimension, so a three-tread quarter turn on a 900mm stair consumes roughly the same material as four straight steps. Count them as such rather than as three.
Converting square metres to roll length
Carpet in metric markets comes on 4m and 5m wide rolls and is priced per linear metre or per square metre. One linear metre of a 4m roll is 4 square metres. Dividing your area by the roll width gives the theoretical length, but stair pieces are cut across the roll so the pile direction runs correctly down each step, which means a 900mm stair uses a 900mm band of a 4m roll. Unless the fitter can use the remaining 3.1m band elsewhere, the invoice will reflect the full width.
- Measure tread, riser and nosing on four steps and take the largest of each.
- Add them for the per-step run in millimetres, then divide by 1000 for metres.
- Multiply by step count and by stair width in metres.
- Add landings as plain rectangles and count each winder as 1.3 straight steps.
- Add 10 per cent waste, or 15 to 20 per cent for a pattern or a turning flight.
- Ask the fitter how they will cut it off the roll before you order linear metres.
Runner instead of full carpet
A runner uses the same per-step run but a narrower width — typically 660mm to 760mm on a 900mm stair, leaving the timber exposed at each side. That is roughly 25 to 30 per cent less material. For a runner you generally want the total length in metres rather than an area, since runners are sold by the running metre, and the stair runner calculator on the home page gives that figure directly along with the per-step breakdown.
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.
Frequently asked questions
How many square metres of carpet do I need for stairs?
Multiply the per-step run — tread plus riser plus nosing, about 0.465m — by the number of steps and the stair width in metres, then add 10 per cent. A 13-step flight at 900mm wide comes to about 6 square metres including waste.
How many square metres is a 13-step staircase?
About 5.4 square metres of bare coverage at 900mm wide, or 6.0 square metres allowing 10 per cent for cutting. Add roughly 0.8 square metres for a standard half landing.
How do I convert square metres to linear metres of carpet?
Divide the square metres by the roll width. On a 4m roll, 6 square metres is 1.5 linear metres in theory — but stair pieces are cut across the roll, so ask the fitter whether the remaining width can be used before ordering on that basis.
How much waste should I allow in metric?
10 per cent for a plain carpet on a straight flight, 15 to 20 per cent where the flight turns or the carpet has a pattern repeat to match.
Is a stair runner measured in square metres?
No, usually in running metres, because runners are sold by length at a fixed width. Work out the total run over all the steps and add a tail top and bottom, then order to the next whole metre.
Know your numbers in 30 seconds
Enter your step count, tread depth and riser height — the stair runner calculator gives you the exact length to order, in metres and feet, with waste included.
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Every guide is written from hands-on measuring and fitting experience, checked against the calculator’s own maths, and re-reviewed whenever prices or methods change. Read our editorial standards.