Stair Stringer Calculator
Example: Total rise (floor to floor): 108 in · Target riser height: 7.5 in · Tread run per step: 10 in
| Number of risers | 14 |
| Number of treads | 13 |
| Actual riser height | 7.71 |
| Total horizontal run | 130 |
Worked example
For a total rise of 108 inches with a target riser of 7.5 inches, 108 / 7.5 = 14.4, which rounds to 14 risers. The actual riser height is then 108 / 14 = about 7.71 inches, uniform across every step. Fourteen risers means 13 treads, and at a 10-inch run each the staircase extends 130 inches horizontally. Always confirm the actual riser against your local code maximum.
Frequently asked questions
What is a comfortable riser and tread?
A widely used comfort rule keeps risers around 7 to 7.75 inches and treads around 10 to 11 inches, and many codes cap the riser at 7.75 inches for interior stairs. The old rule of thumb is that rise plus run should total roughly 17 to 18 inches for a natural stride.
Why must all risers be equal?
The human gait locks onto a rhythm on stairs, so even a small variation between risers is a trip hazard and is limited by code, often to about 3/8 inch of variation across a flight. Dividing the total rise into equal parts, as this tool does, is how you guarantee uniform steps.
How do I find the total rise?
Measure the vertical distance from the finished surface of the lower floor to the finished surface of the upper floor, including any flooring that will be added. Getting this number exactly right is critical, because an error here is spread across every riser in the flight.
Does the stringer length come from this?
The total run and total rise define a right triangle whose hypotenuse is the stringer line. You can get the stringer length from the square root of run squared plus rise squared, then add material for the top and bottom cuts. This tool gives you the run and rise those calculations start from.