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Measure the total rise from the finished floor below to the finished floor above, in inches. Adjust the target riser and tread to see other layouts.
How many steps do my stairs need?
Everything happens on your device: nothing is uploaded to the internet.
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Stair calculator: what it is for
Enter the total rise in inches and your target riser height and tread depth. The calculator rounds to a whole number of risers, gives the exact riser height, the number of treads, the total run, the stair angle and the stringer length, and warns when the riser is over 7 3/4 in or the tread is under 10 in.
It also checks the comfort rules (2 risers + 1 tread between 24 and 25 in) and shows the measurements in fractions of an inch, ready to mark on the stringer.
How to use
- Measure and enter the total rise.
- Set the target riser and tread.
- Read the steps, run and stringer length.
When to use it
- Deck and porch stairs.
- Basement stairs.
- Checking a stair before inspection.
Frequently asked questions
What are the code limits for residential stairs?
The International Residential Code (IRC R311.7.5) sets a maximum riser height of 7 3/4 inches and a minimum tread depth of 10 inches, with no more than 3/8 inch of difference between the largest and smallest riser or tread in a flight. Local codes can differ, so check with your building department.
How do you calculate the number of steps?
Divide the total rise by your target riser height and round up to get the number of risers. Then divide the total rise by that number to get the exact riser height. The number of treads is usually one less than the number of risers.
What is the 7-11 or 17-18 rule?
Two common comfort rules: riser plus tread close to 17 to 18 inches, or two risers plus one tread close to 24 to 25 inches. A 7 in riser with an 11 in tread is the classic comfortable stair.
Is it really free?
Yes, 100% free. No sign-up, no subscription and no usage limits. All Tools123 tools are free and run right in your browser.