Using the Stair Calculator
The calculator rounds the required number of risers up, then recalculates the actual height. It assumes the upper floor serves as the final landing, so there is one fewer tread than risers. Tread depth determines the resulting horizontal run.
Worked example
Use the example inputs below to reproduce this result. These are the form's starting values, not recommended targets. Changing your inputs updates your result above; this worked example stays fixed for comparison. Results are rounded for display.
Example inputs
- Total rise (cm)
- 280
- Desired maximum riser (cm)
- 18
- Tread depth (cm)
- 28
Example result
- Number of risers
- 16
- Actual riser height (cm)
- 17.5
- Number of treads
- 15
- Horizontal run (cm)
- 420
Method and assumptions
Rounds the riser count up and divides total rise evenly. Assumes the upper floor is the final landing. Check local building codes, headroom and landing requirements before construction.
Check the geometry against the available space
A stair calculation can distribute height evenly yet still require more horizontal space than is available. Compare the calculated run with the actual opening and layout. The simplified geometry does not check landings, headroom or every construction requirement. Those constraints need to be resolved before dimensions are treated as a buildable design.
Common question
Why does the actual riser height differ from my entry?
Your entry is the desired maximum, not a height the tool forces exactly. The total rise usually does not divide into that height evenly. Rounding the riser count up allows equal risers without exceeding the selected maximum.
Guide updated .