Stair stringer planning starts with total rise. From there, you estimate the number of risers, the individual rise, the tread run, and the total horizontal run.
Work from Total Rise
Measure the vertical distance from the lower finished surface to the upper finished surface.
Divide that total by a target riser height to estimate the riser count, then adjust until the rise is consistent.
Check the Whole Stair
After rise and run are estimated, check headroom, landing space, tread depth, nosing, stringer stock, and the final built conditions.
Stairs are safety-critical, so use calculator results only as planning estimates.
Stair Stringer Formula
Riser count = round(total_rise / target_riser_height). Actual riser height = total_rise / riser_count.
Tread count = riser_count - 1. Total run = tread_count x tread_depth. Stringer length = square root of (total_rise squared + total_run squared).
Worked Example
A total rise of 2800 mm with a target riser height of 175 mm gives 16 risers. The actual riser height is 175 mm.
With a 270 mm tread depth, tread count is 15, total run is 4050 mm, and the stringer length is about 4.92 m before cut details.
Common Mistakes
Do not measure from unfinished surfaces if the finished floor height will change.
Do not ignore handrails, landings, headroom, tread nosing, stringer strength, safety requirements, or local building rules.
FAQs
What is total rise?
Total rise is the vertical distance between the lower and upper finished walking surfaces.
Are stair calculator results enough to build from?
No. Verify the layout, material, safety requirements, and local rules before building.
Estimates only
These results are estimates only. Verify measurements, material specifications, structural requirements, safety requirements, and local building rules before buying materials or building.