How it works
The number of risers must be a whole integer, so the actual riser height differs slightly from your preferred value. The calculator picks the integer that minimises that difference.
Comfort guidelines
| Stair type | Riser (mm) | Tread (mm) | Slope |
|---|---|---|---|
| Comfortable / domestic | 150 – 180 | 250 – 300 | 26 – 36° |
| Standard | 180 – 200 | 230 – 270 | 33 – 41° |
| Steep / utility | 200 – 220 | 200 – 230 | 40 – 47° |
| Ladder-like (avoid) | > 220 | < 200 | > 47° |
2R + T should fall between 600 and 640 mm for comfortable everyday use.
FAQ
What about landings?
For straight runs over 12 risers, a landing is recommended (and often code-required). U-shape and L-shape stairs naturally include a landing — just split the floor-to-floor height into two flights and run this calculator twice.
How wide should the staircase be?
Residential: minimum 900 mm clear. Comfortable: 1,000–1,200 mm. Public buildings: ≥ 1,500 mm. The calculator doesn't ask for width because it doesn't affect rise/run.
What's "going" vs "tread"?
"Going" is the horizontal distance between two consecutive risers (used in IS code). "Tread depth" is the same thing, including the nosing overhang. Most people use them interchangeably.