Stair Calculator
Free stair calculator. Enter total rise and target riser height to get the number of risers and treads, riser height, run, stringer length and stair angle for a code-compliant staircase.
About This Free Online Stair Calculator
Our free stair calculator takes the guesswork out of building a staircase. Enter the total rise (floor to floor height) and your desired riser height, plus the tread depth, and the tool works out the number of risers and treads, the exact riser height after rounding to a whole number of steps, the total run, the stringer length and the stair angle. Results stay within comfortable, code-friendly ranges so you can lay out stringers confidently. Everything runs in your browser — perfect for deck builders, carpenters and homeowners.
Features of Our Stair Calculator
- Riser and tread count from total rise and target riser height
- Exact riser height after balancing the steps
- Total run from tread depth and count
- Stringer length and stair angle for layout
- Works for interior and deck stairs
- 100% client-side and private — instant results, no signup
How to Use the Stair Calculator
Using this tool is simple and requires no signup or registration. Follow these steps:
- Measure the total rise — floor to floor or deck to ground.
- Set a target riser height (7 to 7.75 in is comfortable).
- Enter the tread depth in inches.
- Read off risers, treads, run, stringer length and angle.
Frequently Asked Questions About Stair Calculator
What is a comfortable riser height?
Most building codes limit risers to about 7.75 in maximum, and the most comfortable stairs have risers between 7 and 7.5 in. Aim for riser plus tread (in inches) to equal about 17 to 18. Enter a target of 7.5 in and the calculator balances the actual height.
How do I calculate the number of stairs?
Divide the total rise by your target riser height and round up to a whole number — that is your riser count. The treads are one fewer than the risers. The calculator does this and then gives the exact riser height for that step count.
How long is a stair stringer?
The stringer length is the diagonal (hypotenuse) of the total rise and total run — the square root of rise squared plus run squared. Add length for landing cuts. The calculator returns the stringer length and the angle for laying out your cuts.
How deep should a tread be?
A comfortable tread is about 10 to 11 inches deep (minimum 10 in is common in codes). Deeper treads suit gentler stairs. Enter your tread depth and the calculator uses it for the total run.
Is this stair calculator free?
Yes, completely free with no signup. All maths runs in your browser — nothing is uploaded or tracked.
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