Stair Runner Length CalculatorStair type
Stair runner length calculator for box stairs
A box stair is closed on both sides — walls or full stringers — so there is no exposed edge to design around. The length calculation is the same as a straight flight, but the width decision changes.
Measure wall to wall at the narrowest point, because plaster is rarely parallel.
Stair runner calculator
Your stair runner length
20 ft 3.1 in
Total runner required for 13 steps, including a 10% waste allowance.
| Inches | 243.1 in |
|---|---|
| Feet | 20.26 ft |
| Feet & inches | 20 ft 3.1 in |
| Yards | 6.75 yd |
| Meters | 6.17 m |
| Centimeters | 617.47 cm |
Recommended purchase length
21 ft
7 yd · 6.4 m · 252 in
This calculator provides an estimate based on the measurements and installation assumptions you enter. Complex, curved or winder staircases may require professional measurement.
Your measurements, drawn to scale
Length is straightforward
Steps × (tread + riser), plus nosing and waste. Box stairs are almost always uniform, so a single tread measurement checked against two others is enough.
Width and reveal on a closed stair
You can either fit a runner with a deliberate reveal each side or fit wall-to-wall carpet. If you want a runner look, measure the narrowest point and subtract at least 6 in total so the runner clears the plaster all the way up.
No binding on the wall side?
Both long edges are still visible on a runner, so both still need binding or serging. Only a full wall-to-wall fit escapes that.
Questions people ask
- What width runner for a box staircase?
- Measure wall to wall at the narrowest point and subtract 6 to 10 in total so you keep an even reveal even where the walls are out of square.
- Is the length calculation different for box stairs?
- No. Length is steps × (tread + riser) plus allowances, exactly as for an open straight flight.