Stair calculator
Measure the total rise from the landing surface to the top surface. The calculator splits it into equal steps and gives the measurements in fractions.
Steps (risers)
5 risers of 7 3/16 in
- Riser height
- 7 3/16 in (7.2)
- Treads
- 4 treads
- Total run
- 3 ft 4 in
- Stringer length
- 4 ft 5 13/16 in minimum
- Stair angle
- 35.8 degrees
How it works
The calculator divides the total rise by your maximum riser height and rounds up to get the number of risers. It then divides the rise evenly among them, so every step is the same height. That matters: uneven steps are a classic trip hazard.
When the top tread is the deck or floor itself, a stair has one fewer tread than risers. Total run is treads × tread depth, and the stringer length is the diagonal of the rise and run. Buy stringer stock longer than that to allow for the top and bottom cuts.
Example
With total rise 36 in, maximum riser height 7.75 in, tread depth 10 in, the answer is 5 risers of 7 3/16 in.
Tips before you buy
- US residential code (IRC) limits risers to 7¾ inches and requires treads of at least 10 inches. Your local code may differ, so check it.
- Riser heights within one flight shouldn’t vary by more than 3/8 inch.
- Measure the rise at the exact spot where the bottom of the stairs will land. Sloped ground changes the number.
- A common comfort rule: two risers plus one tread should add up to about 24–25 inches.
Common questions
How many steps do I need for a 36-inch rise?
Five risers of 7 3/16 inches each, with four treads.
What is the difference between rise and run?
Rise is the vertical height of each step. Run is the horizontal depth of each tread.
Why does a stair have one fewer tread than risers?
The top step is the deck or upper floor itself, so it doesn’t need a separate tread.