Stair calculator: Find the number of steps, rise and stair length
A staircase must fit both the height difference and the space available. Here you can look at possible combinations of number of steps, rise and tread and see the measurements on a simple drawing.
Worked example
- Height between finished floors: 110.2362 in
- Number of risers: 16
- Going: 11.0236 in
Rise
6.8898 in
16 risers and 15 treads · run 165.3543 in · pitch 32.0054 degrees · step rule (2 × rise + going) 24.8031 in
| Risers | Rise | Run | Slope |
|---|---|---|---|
| 14 | 7.874 in | 143.3071 in | 35.5377 ° |
| 15 | 7.3491 in | 154.3307 in | 33.6901 ° |
| 16 | 6.8898 in | 165.3543 in | 32.0054 ° |
| 17 | 6.4845 in | 176.378 in | 30.4655 ° |
| 18 | 6.1242 in | 187.4016 in | 29.0546 ° |
The upper floor is the last step, so there is one tread fewer than the number of risers. Geometric planning, not an approval under the rules for the project.
Start with the height between finished floors
Measure the height from the lower finished floor to the upper one. The floor build-up can change the measurement if you measure before the flooring is laid. Then enter the horizontal space the staircase may use.
The calculator shows its counting method. The number of risers and the number of horizontal treads are not necessarily the same. When the upper floor serves as the last step, there can, for example, be one tread fewer than the number of risers.
Guide to looking at a staircase
Compare several numbers of steps
An extra step changes the rise and can require a different tread. Use the drawing to see how the possible solutions fit in the room. Comfort measurements are shown as guidance with the chosen method.
Example with 16 risers
A height of 2,800 mm divided into 16 risers gives 175 mm per riser. With 15 treads of 280 mm, the horizontal run is 4,200 mm under this counting convention.
The result is geometric planning. Headroom, guards, handrails, use and construction must be assessed according to the rules that apply to the project. An internal staircase in a home and a shared access staircase can have different requirements. So use the calculation to prepare drawings and quotes, not as an overall approval of the staircase.