About this calculator
The calculator checks the common comfort rule that twice the riser plus the tread should be 550 to 700 mm.
How to use it
- Enter the floor-to-floor height.
- Enter the maximum riser and tread.
- Enter the stair width.
The formula
Risers = height ÷ maximum riser, rounded up; actual riser = height ÷ risers
- tread
- horizontal depth of each step
- 2R + T
- comfort rule, 550 to 700 mm
Worked example
A 3,000 mm floor height with 175 mm maximum riser
- 18 risers of 166.7 mm and 17 treads of 250 mm.
- Total going 4.25 m; angle 33.7°.
- 2 × 166.7 + 250 = 583 mm, comfortable.
What the result means
Landings break long flights and are often required after about 12 to 15 steps.
Assumptions
- Straight flight.
Limitations
- Have stairs designed by an engineer; check local building rules.
Frequently asked questions
What is the standard riser height?
For homes, the National Building Code allows up to 190 mm; 150 to 175 mm is comfortable.
How wide should stairs be?
At least 900 mm to 1 m in most homes.
What is a good stair angle?
About 30° to 37°.
Last reviewed on 3 October 2026. Found a mistake? Tell us.