How to use this calculator
- Enter total rise. Measure finished floor-to-floor, deck-to-grade or landing-to-landing height.
- Choose a target riser. Use a comfortable target height to choose the number of risers.
- Enter tread run. Use the horizontal tread depth before nosing details.
- Check margins. Compare the actual riser and tread run with your local code and plan set.
How it works
Riser count is rounded up from total rise divided by the target riser height:
risers = ceil(total_rise / target_riser)
Actual riser height is then fixed by the total rise:
actual_riser = total_rise / risers
For a stair ending at an upper landing, tread count is one less than riser count:
treads = risers - 1
total_run = tread_run x treads
stringer_length = sqrt(total_rise^2 + total_run^2)
The stair stringer chart uses the same rise/run workflow while the calculator handles rounding and exact layout. For exact query wording, use the stair stringer calculator for rise and run.
Worked example
Verified against the live calculator
A 108 in total rise with a 7.25 in target riser
gives 15 risers. The actual riser is 7.2 in,
with 14 tread runs. At a 10 in tread run, total
run is 140 in and the stringer length is about
14.7 ft.
Frequently asked questions
How do you calculate stair stringer rise and run?
Choose the riser count by rounding total rise divided by target riser height up to the next whole riser. Actual riser height is total rise divided by that riser count. Total run is tread run times one fewer tread than risers.
Why are treads one less than risers?
For a stair that ends at an upper floor or landing, the landing acts as the final walking surface. The number of tread cuts in the stringer is usually risers minus one.
Does this check stair code?
No. It only screens layout geometry. Final stairs still need local code checks for riser/tread limits, uniformity, nosing, headroom, landings, handrails, guards and attachment.
Does this size the stringer structurally?
No. Stringer strength, notch depth, support, hangers, bearing, fasteners and framing design are not included.
Method & assumptions
- Assumes a straight stair between two finished levels.
- Counts one fewer tread than risers because the upper floor or landing is the final walking surface.
- Does not check code, nosing, headroom, landings, handrails, guards, stringer strength, notch limits, hangers or permits.
- Use the stair stringer rise and run page, rafter layout, board feet and wood span for adjacent carpentry planning checks.