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Easily calculate stair rise, run, angle & stringer length with our free stair calculator. Accurate, code-compliant, and perfect for any stair project.
Designing a staircase can be tricky, especially if you're unsure how to calculate the right rise and run. That’s why we’ve developed this Stair Rise and Run Calculator a simple yet powerful tool that helps you create stairs that are safe, comfortable, and code-compliant.
Whether you're a contractor, architect, carpenter, or a homeowner doing a DIY project, our calculator takes the guesswork out of stair planning. It's based on proven ergonomic and building code standards, ensuring every step feels just right.
The "rise" of a stair is the vertical height of each step, and the "run" is the horizontal depth or length of each tread. Together, these two measurements determine the angle, safety, and comfort of your staircase.
Too steep? The stairs become unsafe. Too shallow? They take up too much space and feel awkward. That’s where our calculator comes in to help you find the perfect balance.
When you enter your total rise (the vertical height from the lower floor to the upper floor), your ideal riser height, and your tread depth, the calculator does the rest. It instantly provides:
Everything is calculated using international best practices and ergonomic standards.
We use these simple and accurate formulas to calculate your stairs:
1. Number of Risers
Number of risers = Total rise ÷ Ideal riser height
(Rounded up to ensure no step exceeds the ideal)
2. Unit Rise
Unit rise = Total rise ÷ Number of risers
3. Number of Treads
Number of treads = Number of risers − 1
4. Total Run
Total run = Tread depth × Number of treads
5. Stringer Length
Stringer length = √(rise² + run²)
6. Angle of Stair
Angle = arctangent(rise ÷ run), converted to degrees
7. Comfort Formulas
R + G ≈ 17–18 inches
R × G ≈ 75 ± 3 inches²
2R + G ≈ 25 ± 1 inches
These ergonomic rules help ensure the stairs are not too steep or too flat.
Simply input your measurements into the form:
The calculator automatically checks for ergonomic comfort and building code compliance. It even converts your results into your chosen unit.
Stair planning is no longer complicated. Our Stair Rise and Run Calculator gives you everything you need to design perfect stairs that follow safety regulations and feel right underfoot. Whether you're working on a home, deck, or commercial building, this tool helps save time, reduce errors, and improve results.
We’ve made the calculator free, easy to use, and fully responsive on mobile. No math headaches, no codebooks just accurate stair design in seconds.
It’s an ergonomic rule stating that the sum of riser height and tread depth should equal around 17 to 18 inches for comfort.
Ideally, the rise should be between 6.5–7.5 inches (165–190 mm), and the run (tread depth) should be at least 10 inches (250 mm).
The "27 rule" combines the rise and tread depth of exterior stairs, recommending that twice the rise plus the run equals about 27 inches.
Nosing improves safety and comfort. Building codes often require nosing if the tread is under a certain depth.
Yes! The calculator supports inches, feet, centimeters, millimeters, and meters.
Yes, it checks the riser height (≤7.75") and tread depth (≥10") against common residential code standards.