Calculation details
Planning estimate only. Verify dimensions, waste, coverage, product specifications, and local requirements before purchasing materials.
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Use this result
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What does this calculator estimate?
A 60-inch total rise with a 7.5-inch target riser produces 8 risers, so 7 treads with a run of about 10 inches each (a 70-inch total run). Risers = ceiling(total rise / target riser); treads = risers - 1.
- Building codes typically cap risers at about 7.75 inches (IRC).
- Treads = risers - 1 because the top landing ends the stair.
- Stringer length uses the square root of rise squared plus run squared.
How stair math works
Stairs are defined by risers (vertical) and treads (horizontal). The total rise divided by the riser height gives the riser count; the run is the treads times their depth. Code limits riser height and minimum tread depth for safety.
Limitations to watch for
Local codes differ — the tool uses common US residential limits (7¾" max riser, 10" min tread) but check yours. Consistent riser heights are critical (variation causes trips). The tool doesn't model landings, headroom, or stringer cuts.
How to use it in practice
Measure the total rise floor-to-floor. Choose a riser height (7–7.5" is comfortable) and let the tool compute risers and run. Verify the run fits your space; add a landing for long runs. Use the numbers to cut stringers and order materials.
['Enter the total rise.', 'Enter the target riser height and tread depth.', 'Read riser count, tread count, and total run.']
How this calculator works
Formula
Risers = total rise ÷ riser height (rounded). Treads = risers − 1. Run = treads × tread depth. Building codes typically require risers ≤ 7¾" and treads ≥ 10".
Worked example
A 108-inch rise with 7-inch risers: 15 risers (14 treads), a run of 154 inches at 11-inch treads.
Assumptions to verify
- US residential code limits apply.
- The stair is a straight run.
- Riser heights are consistent.
Frequently asked questions
How do I calculate stairs?
Rise ÷ riser height = risers; treads = risers − 1; run = treads × depth. A 108" rise at 7" risers = 15 risers.
What is the maximum riser height?
7¾" under most US residential codes.
What is the minimum tread depth?
10" under most codes.
How many treads do I need?
One fewer than risers — the top floor is the last 'tread'.
Why must risers be consistent?
Varying riser heights cause trips — code limits variation to 3/16".
What is the stair run?
The total horizontal length: treads × depth. 14 treads × 11" = 154".
Do I need a landing?
Yes, for long runs or where the run exceeds the available space — typically every 12 feet or at direction changes.
Cite this tool
BoringToolsKit. “Stair Calculator.” boringtoolskit.com/stair-calculator/ (reviewed 2026-08-25). Free to reference in articles, syllabi, and answer posts with a link.
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