Calculate Stair Rise, Run and Angle
Calculate stair angle from one step, an entire flight or a design target. See actual riser height, tread depth, total run, stringer length, slope and the 2R + T comfort check in a live staircase diagram.
Measurement mode
Dimensions
Reference checks
Stair geometry result
How to calculate or figure out a stair angle
Divide vertical rise by horizontal run, then apply the inverse tangent. The same ratio can come from one representative step or from the entire flight. A stringer is the hypotenuse of the total-rise and total-run triangle.
Design mode
Design mode divides total rise into a whole number of equal risers. It rounds the riser count upward so the actual riser does not exceed the entered target, then uses one fewer tread than risers for a typical floor-to-floor flight.
Stair stringer, railing and trim angles
The displayed flight angle is also the primary slope reference for a straight stringer and a railing that follows the stair pitch. Compound cuts, landing transitions, posts, nosings and molding profiles may require additional project-specific angles.
2R + T check
The common comfort relationship adds twice the riser height to tread depth. It is a design aid, not a universal code rule. Landings, nosings, headroom, handrails, guards, width, consistency and local amendments still require project-specific review.
What stair angle is comfortable?
Many residential stairs fall roughly in the 30–37 degree range, but geometry and legal requirements vary. Use the editable range as a planning comparison only.
Are the number of treads and risers equal?
For a typical floor-to-floor flight, there is usually one fewer tread than risers because the upper floor acts as the final walking surface.