Stair Tread Calculator
Find the number of risers and treads, the riser height and the total run for a staircase.
Recent
Formula
How the calculation works
The total rise in inches is divided by a comfortable step height of about seven inches to count the risers.
The treads are one fewer than the risers, because the top step lands on the upper floor itself.
Adding the nosing to each tread gives the total run including the small overhang that makes a stair comfortable.
Common mistakes
- Forgetting the last riser, which leaves the stair a step short of the floor.
- Making risers too tall to be comfortable: anything well over seven inches is tiring and unsafe.
When to use it
- Use it when planning a staircase to check the step height and total run fit the space.
- It is not a structural design; building codes and headroom need a professional check.
Worked example
A 9 ft rise with 10 in treads and 1 in nosing gives 15 risers, 14 treads, a 7.2 in riser and a 140 in run (154 in with nosing).
Common questions
Why is there one fewer tread than riser?
The top step is the floor itself, so a run of 15 risers has only 14 treads.
Is a 7.2 in riser comfortable?
Yes, risers between 7 and 7.5 inches are comfortable for most homes.
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