Stair Calculator
Steps, riser height, tread depth, run, and stringer from total rise
Steps
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Frequently Asked Questions
How do I calculate the number of stairs?
Divide the total rise (floor-to-floor height) by a comfortable target riser height — about 7 inches — and round to the nearest whole number. That is your number of risers (steps). The number of treads is one less than the number of risers.
What is a comfortable riser height and tread depth?
Most codes cap riser height around 7¾ inches and require tread depth of at least 10 inches. A widely used comfort rule is 2 × riser + tread ≈ 25 inches, which this calculator uses to pair a tread depth with your riser height.
Why must all the risers be equal?
Uneven risers are a major trip hazard and a common code violation. Codes typically allow no more than about 3/8 inch variation between the largest and smallest riser in a flight. Dividing the total rise evenly guarantees uniform steps.
What is the stringer length?
The stringer is the diagonal board that supports the steps. Its length is the hypotenuse of the rise and run: √(total rise² + total run²). Add extra material for the cuts and connections at the top and bottom.
What angle should a staircase be?
Comfortable interior stairs are usually between about 30° and 37°. Steeper than ~42° feels ladder-like and may not meet code. This calculator reports the resulting angle so you can adjust the riser height if needed.