How to Use This Tool
Solve a whole-number riser layout before marking a stringer board. Calculate stair riser count, exact riser height, total run and diagonal stringer length from editable project dimensions.
The decision this tool supports
Rounding a decimal riser count instead of resolving a whole number makes the last step a different height and can create a serious trip hazard. This page keeps the decision bounded to number of risers and the supporting outputs shown beside it. Stair Stringer does not import an account, infer a market rate, or silently substitute an industry average.
Inputs and units
The Stair Stringer calculation uses Total vertical rise, Maximum target riser, Tread run. Keep all money values in one currency and all time, distance, mass, energy or volume entries in the unit printed beside the field. Mixing Stair Stringer scopes can produce a plausible number with the wrong meaning.
- Total vertical rise is entered in inches.
- Maximum target riser is entered in inches.
- Tread run is entered in inches.
Formula and worked check
Risers = ceiling(total rise ÷ maximum target riser); exact rise = total rise ÷ risers; treads = risers − 1; diagonal = √(rise² + run²). A 108-inch rise with a 7.75-inch maximum target produces 14 risers at 7.71 inches, 13 ten-inch treads, 130 inches of run and a 169.01-inch diagonal. The Stair Stringer default is an executable known-answer case, not a benchmark or recommendation. Change one input and verify that the direction of number of risers still matches the stated relationship.
How to interpret the result
Use exact rise and run to draft the geometry, then verify every local residential or occupational rule, landing, headroom and finish-thickness adjustment. The additional Stair Stringer outputs expose the denominator, comparison, capacity or reverse value needed to audit the primary result instead of presenting one unexplained number.
Assumptions
- Top and bottom finish elevations define total rise.
- One fewer tread than risers is used for a stair ending at an upper floor.
- Local code and actual board geometry remain authoritative.
Save the Stair Stringer input values and date with any material decision. A later Stair Stringer rerun is reproducible only when the same assumptions and units are available.
Limitations and safety boundary
This geometry tool is not a code-compliance or structural design service and does not size lumber, cuts, landings, guards or fasteners. Stair Stringer is an estimate and cannot replace a contract, local code, licensed professional, calibrated measurement, lender statement or platform report where one governs the decision.
Source and privacy
The Stair Stringer definition or rule was checked against OSHA — 29 CFR 1910.25 Stairways on 2026-08-26. Recheck OSHA — 29 CFR 1910.25 Stairways when a specification or policy behind Stair Stringer can change. Stair Stringer arithmetic runs in this browser tab; ecech does not receive the values through a calculation API.
Sources & assumptions
Tool Spec v2 · verified 2026-08-26. Platform rules and fees can change; the editable inputs remain authoritative for your account.
Official references
- OSHA — 29 CFR 1910.25 Stairways (checked 2026-08-26)
Model assumptions
- Top and bottom finish elevations define total rise.
- One fewer tread than risers is used for a stair ending at an upper floor.
- Local code and actual board geometry remain authoritative.
- This geometry tool is not a code-compliance or structural design service and does not size lumber, cuts, landings, guards or fasteners.
