Calculate stair risers, actual riser height, tread layout, and total run from your project dimensions.
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Risers, treads, and total run from your total rise.
Stair layout starts with the total vertical rise between the lower and upper finished floor levels. Divide the total rise into equal risers that do not exceed the selected maximum riser height. Once the number of risers is known, the tread depth can be used to calculate the stair’s total horizontal run.
Risers = Ceiling(Total Rise ÷ Max Riser)
Actual Riser Height = Total Rise ÷ Risers
Treads = Risers − 1
Total Run = Treads × Tread Depth
The calculator rounds the number of risers up to a whole number so the actual riser height does not exceed the selected maximum.
A stair with a 108 in total rise, a 7 3/4 in maximum riser, and 10 1/2 in treads:
108 ÷ 7.75 = 13.94
Round up to a whole number
14 risers108 ÷ 14 = 7.714 in
Actual rise: ≈ 7 11/16 in per riser14 − 1 = 13 treads
13 × 10.5 = 136.5 in
Total run: 136 1/2 in = 11 ft 4 1/2 inThe vertical distance from the lower finished floor to the upper finished floor.
The vertical height of each individual stair step.
The horizontal depth of each stair tread used to determine the stair run.
The horizontal distance occupied by the stair from the first tread to the upper level.
| Measurement | Relationship |
|---|---|
| Number of risers | Total rise ÷ target/max riser, rounded up |
| Actual riser | Total rise ÷ number of risers |
| Number of treads | Typically risers − 1 between floors |
| Total run | Number of treads × tread depth |
| 12 inches | 1 foot |
Divide the total rise by your target or maximum riser height, then round up to the next whole number. Divide the total rise by that number to determine the actual equal riser height.
Divide the total vertical rise by the calculated number of risers. Each riser should be laid out at the resulting equal height.
For a typical stair connecting two floor levels, there is usually one fewer tread than risers because the upper floor serves as the final walking surface.
Multiply the number of treads by the tread depth. For example, 13 treads at 10 1/2 inches each produce a total run of 136 1/2 inches, or 11 feet 4 1/2 inches.
Maximum permitted riser height depends on the building code and project type that apply to the stair. Enter the appropriate maximum for your project and verify the final layout with local requirements.
Required tread depth varies by code and stair type. Enter the tread depth appropriate for your project and verify the completed design against applicable requirements.
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