Stair Stringer Calculator
Lay out a staircase (riser count and height, tread depth, total run, stringer length, and angle) from the total rise, with IRC riser and tread checks. Calculates in your browser.
Stringer length
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Show the math
Risers divide the rise; the stringer is the hypotenuse of rise and run:
risers = total rise ÷ target riser, rounded up
stringer = √(total rise² + total run²)
The International Residential Code (R311.7.5) allows risers of at most 7¾ in and requires treads of at least 10 in; anything outside those limits is flagged. Rounding the riser count up keeps every riser at or below your target. Verify against your local code. All math runs locally in your browser.
What this does
A stair stringer calculator lays out a staircase (riser count and height, tread depth, total run, stringer length, and angle) from the total rise, with IRC riser and tread checks.
How to use it
- Enter the total rise.
- Set a target riser height.
- Set the tread depth.
- Read the layout and stringer length.
How it works
The riser count is the total rise divided by your target riser, rounded up so no riser is taller than the target, and the stringer is the hypotenuse of rise and run. The IRC allows risers of at most 7¾ inches and treads of at least 10 inches.
stringer = √(rise² + run²)
Understanding your result
The layout is checked against the IRC riser and tread limits, and consistency is the safety point: people climb stairs on autopilot, so even a small variation between riser heights is a genuine trip hazard. Keep every riser and tread equal, confirm the headroom above the run, and verify the final dimensions against your local building code before cutting.
Example
A 9-ft total rise gives about 15 risers at 7.2 inches each.
Sources & methodology
- International Residential Code (2012), R311.7.5 Stair treads and risers, Maximum riser 7¾ in (196 mm); minimum tread 10 in (254 mm)
Last updated .
Frequently asked questions
What is a comfortable riser height?
The International Residential Code allows risers of at most 7¾ inches (R311.7.5.1); 7–7.5 inches feels comfortable. The tool flags any riser above 7¾ inches.
How deep should a tread be?
The International Residential Code requires a tread depth of at least 10 inches (R311.7.5.2); 10–11 inches is typical and comfortable. The tool flags treads under 10 inches.
How is the stringer length found?
It is the hypotenuse of the total rise and total run (√(rise² + run²)) which is the length of board to cut.
Is anything stored?
No. Everything is calculated locally in your browser.
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