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Stair Calculator
Find riser height, tread count, run and stringer length from the total rise, with a code check.
Stair calculator
Risers: — at —
Treads: — · Total run: —
Stringer length: —
—
—
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How to use the Stair Calculator
- Enter the total rise from floor to floor.
- Set the maximum riser height and the tread depth you want.
- Read the riser count, riser height, run and stringer length.
Features
- Riser height from total rise and maximum riser
- Tread count, total run and stringer length
- Code check on riser height and tread depth
- Inches or centimetres with any tread depth
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Frequently Asked Questions
Common questions about the free online stair calculator.
Divide the total rise by the number of risers. Use risers = total rise / maximum riser
rounded up, then divide again for even steps.
The number of treads is always one less than the number of risers, because the top landing
acts as the final step of the flight.
Most codes cap riser height at 7.75 inches (197 mm) and require every riser in a flight to be
within 3/8 inch of the others.
Codes usually require a tread depth of at least 10 inches (254 mm) measured nosing to nosing,
with 11 inches more comfortable.
Use the Pythagorean theorem, stringer = sqrt(total rise squared + total run squared), then
allow extra for the top and bottom cuts.
Comfort usually follows 2 x riser + tread = 24 to 25 inches. A 7 inch riser with an 11 inch
tread gives 25 and feels natural.
Plan for at least 6 feet 8 inches of headroom measured vertically from the nosing line to
anything above the flight.
Most codes require at least 36 inches (914 mm) of clear width, and 44 inches where the stair
serves more than one dwelling.
Yes. Choose centimetres for the total rise and the tool reports riser height, run and
stringer length in the same unit.
Last updated: October 10, 2026