Construction & Materials · Verified formula
Stair Calculator
Calculate riser height, tread depth, stringer length and stair angle from your total rise.
Formula verified
3+ known-answer test cases
Last verified August 2026
Result
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How to use the Stair Calculator
- Measure the total rise — the full vertical height from lower floor to upper floor.
- Enter your target riser height; 7-7.75 in is typical for residential stairs.
- Enter tread depth and nosing overhang, or use the defaults.
- Select Calculate to see riser count, tread count, run and stringer length.
Formula
Risers, treads and stringer
Risers = round(total rise ÷ target riser height) Treads = risers − 1 (typical) Stringer length uses the Pythagorean relationship between total rise and total run
Assumptions: Riser and tread dimensions must meet your local building code — this tool provides a planning estimate, not a code compliance check. This tool provides a general estimate, not professional, engineering, tax or legal advice.
Worked example
Verified example
QA passed
Total rise: 105 in Target riser height: 7.5 in Risers = round(105 ÷ 7.5) = 14 Actual riser height = 105 ÷ 14 = 7.5 in Result: 14 risers at 7.5 in
Why this matters: Riser height directly affects both code compliance and everyday safety — inconsistent riser heights within a single staircase are a well-documented cause of trips.
Common mistakes
- Rounding riser height instead of recalculating it so every riser in the run ends up equal.
- Forgetting that tread count is typically one fewer than riser count, since the top riser lands on the upper floor level.
- Not subtracting nosing overhang from tread depth when calculating total run, which understates how much floor space the staircase needs.
Frequently asked questions
What is a comfortable riser height for stairs?
Most residential building codes call for risers between about 7 and 7.75 inches, with all risers in a single run kept as close to equal as possible.
How many treads does a staircase with 14 risers have?
Typically one fewer than the riser count, since the top riser lands on the upper floor level rather than a separate tread.
How do I calculate stringer length?
Treat total rise and total run as the two legs of a right triangle; the stringer length is the hypotenuse, found with the Pythagorean theorem.
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