How the stair calculator works
It divides the total rise by the maximum riser height of 7¾ inches and rounds up, so every step stays within that limit. All risers are then made equal. There is always one fewer tread than risers, because the top floor acts as the last step. The total run is the number of treads × the tread depth, and the stringer length comes from the rise and run as the sides of a right-angled triangle.
Comfortable step sizes
A common rule of thumb is that riser + tread should come to about 17 to 18 inches. For example, a 7.5 inch riser with a 10 inch tread is 17.5. Steeper stairs save space but are harder to climb; very shallow ones feel awkward. Keep every riser the same height, because people notice even small differences and can trip.
Frequently asked questions
How many steps for a 9 foot ceiling?
For a total rise of 108 inches, 14 risers of about 7.7 inches each, with 13 treads.
What is the maximum stair riser height?
The US International Residential Code allows up to 7¾ inches with treads of at least 10 inches. Commercial buildings and other countries have different limits.
Does the stringer length include the top and bottom cuts?
No. Buy stringer boards longer than the result to allow for the plumb and level cuts at each end.