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Stair Calculator
Enter your total rise (floor-to-floor height) to get the number of steps, the exact riser height, and the tread depth — with an automatic check against IRC limits of a 7¾-inch maximum riser and 10-inch minimum tread.
Change any measurement to update your estimate.
- Riser height
- 7.2 in
- Number of treads
- 14
- Total run
- 147 in
Field notes
Consistency is a safety issue, not a nicety — the code limits the variation between the tallest and shortest riser in a flight to ⅜ inch, because an uneven step is exactly where people trip. Size the whole flight from the total floor-to-floor rise, divide into equal risers near 7 inches, and never fudge the last step to make the math close. Measure the rise in three spots; floors are rarely level.
How the stair calculator works
The math behind the tool:
steps = round(total rise ÷ 7)
riser = total rise ÷ stepsSources: International Code Council (IRC) (residential stair riser/tread code limits).
Frequently asked questions
How do you calculate stair rise and run?
Divide the total floor-to-floor rise by a target riser near 7 inches and round to a whole number of steps, then divide the total rise by that step count for the exact riser height. Treads are typically 10–11 inches deep.
What is the maximum riser height by code?
The International Residential Code sets a maximum riser height of 7¾ inches and a minimum tread depth of 10 inches for residential stairs.
How do you calculate stair stringers?
Work out the riser count and total run first, then the stringer is the hypotenuse: √(total rise² + total run²). A 96-inch rise with a 140-inch run gives a stringer about 170 inches long. Buy stock a foot longer — the top and bottom cuts eat length you cannot get back.
How do you calculate stair risers?
Divide the total floor-to-floor rise by 7 inches, round to the nearest whole number, then divide the rise by that count to get the exact riser height. Every riser must be within 3/8 inch of the others, and the IRC caps riser height at 7¾ inches.
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Step-by-step guides
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