Lay out a staircase that feels right.
Enter your floor to floor height and see the whole stair: how many steps, the exact riser height, tread depth, total run and the stringer board to buy. Every number is checked against US building code as you type.
The staircase
The number of risers is set to hit your target height as closely as possible. A 7 inch riser with an 11 inch tread is the classic comfortable stair.
Does this stair work?
Rise against run
The side profile of your staircase
The build numbers
Riser count options
A few step counts around the ideal, so you can see how riser height, tread and the 2R+T comfort score change. The 2R+T total should land between 24 and 25 inches.
| Risers | Riser height | Tread depth | 2R+T | Total run | Comfort |
|---|
Stairs, explained
How Stairs Are Calculated
The calculator divides the total rise by an ideal riser height (about 7 inches) to determine the number of steps. The actual riser height is the total rise divided by the number of steps. Tread depth is the total run divided by the number of treads (one fewer than risers).
Building Code Requirements
The International Residential Code requires riser heights between 4 and 7.75 inches, with tread depths of at least 10 inches. Stair width must be at least 36 inches, and headroom at least 6 feet 8 inches. Risers must be consistent within 3/8 inch.
Comfortable Stair Dimensions
The most comfortable stairs follow the rule: 2 x riser height + tread depth = 24 to 25 inches. A 7-inch riser with an 11-inch tread (2x7 + 11 = 25) is widely considered ideal. Steeper stairs are tiring; shallower stairs feel unnatural.
Stair Angle and Safety
Residential stairs typically have an angle between 30 and 37 degrees. Angles below 20 degrees feel like ramps, while angles above 45 degrees are more like ladders. The stair angle is calculated from the ratio of total rise to total run.
Common questions
What is the ideal riser height?
The ideal riser height is between 7 and 7.5 inches for residential stairs. Building codes allow up to 7.75 inches. Risers must all be the same height within 3/8 inch to prevent tripping.
What is the minimum tread depth?
Building codes require a minimum tread depth of 10 inches, measured from the front edge (nosing) of one tread to the front edge of the next. Most comfortable stairs have treads of 10 to 11 inches.
How do I measure total rise?
Measure the vertical distance from the finished floor at the bottom to the finished floor at the top. Include any flooring thickness that has not been installed yet, as this affects the final riser heights.
What if my stairs do not meet code?
If the calculated dimensions fall outside code limits, adjust the total run (horizontal distance) to achieve compliant tread depths and riser heights. Adding or removing a step can also bring dimensions into compliance.
Estimates for planning only. Building codes vary by state and locality, and finished floor thickness changes your real riser heights. Confirm every dimension against your local code and have your layout checked before you cut a stringer.