The formula
Total length = steps × (tread depth + riser height + nosing allowance) + landings + winder allowance + pattern allowance + waste.
- Tread depth: front edge to the riser behind, measured on the deepest tread.
- Riser height: the vertical face between treads.
- Nosing allowance: 2–5cm per step for a wrapped (Hollywood) fit; zero for a waterfall fit.
- Landings: the full depth of each landing, plus 10–15cm tuck per piece.
- Winders: treat each pie step as a full step and add 15–20% on the turn.
- Pattern allowance: one full repeat per separate piece.
- Waste: 5% straight flights, 10% with turns or bold patterns.
Worked example — 13-step straight flight
| Element | Calculation | Result |
|---|---|---|
| Tread depth | 27cm × 13 | 3.51m |
| Riser height | 19cm × 13 | 2.47m |
| Nosing wrap | 3cm × 13 | 0.39m |
| Subtotal | 6.37m | |
| Waste at 5% | 6.37 × 1.05 | 6.69m |
| Purchase length | Round up | 7.0m |
Always round up to the next half metre
Suppliers cut to order, and returning a custom cut is usually impossible. A spare 30cm costs a few pounds; being 30cm short costs a whole new order from a different batch.
Worked example — 16 steps with a half landing
| Element | Calculation | Result |
|---|---|---|
| Steps (28cm tread + 18cm riser + 3cm nosing) | 49cm × 16 | 7.84m |
| Landing 1.0m deep + 0.15m tuck | 1.15m | |
| Pattern repeat, 2 pieces × 0.4m | 0.80m | |
| Subtotal | 9.79m | |
| Waste at 10% | 9.79 × 1.10 | 10.77m |
| Purchase length | Round up | 11.0m |
The allowances people forget
- The bottom step is often deeper (a bullnose or curtail step) — measure it separately.
- The top nosing needs runner over it and onto the landing, typically 5–8cm.
- Winders eat material because each piece is cut from the widest point of the wedge.
- Pattern repeats apply per piece, not per staircase.
- Pile direction means offcuts often cannot be reused elsewhere on the same flight.
Quick reference
| Staircase | Typical order length |
|---|---|
| 12 straight steps | 6.0–6.5m / 20–21ft |
| 13 straight steps | 6.5–7.0m / 21–23ft |
| 14 straight steps | 7.0–7.5m / 23–25ft |
| 16 steps with landing | 10.5–11.5m / 34–38ft |
| 13 steps with 3 winders | 8.0–9.0m / 26–30ft |
Treat these as sanity checks only. Tread depths vary by 5cm or more between houses, and that difference alone moves a 13-step flight by nearly a metre — which is why it is worth entering your own measurements rather than trusting a table.
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 calculatorWhatever 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.
Frequently asked questions
How much stair runner do I need for 13 stairs?
Around 6.5–7.0m (21–23ft) for typical dimensions of a 27cm tread, 19cm riser and a wrapped nosing, including 5% waste. Measure your own treads, though — depth varies enough to change the answer by nearly a metre.
How do you calculate stair runner length?
Multiply the number of steps by the sum of tread depth, riser height and nosing allowance, then add landing depths, winder allowance, one pattern repeat per piece and 5–10% waste.
How much extra runner should I allow for waste?
5% on a straight flight with a plain runner, and 10% where there are landings, winders or a bold pattern that must be matched.
Does the runner need to go over the top step?
Yes — allow 5–8cm to run over the top nosing and onto the landing so the edge is fixed on a flat surface rather than on the nosing itself.
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.
Run the numbers automatically