Stair Calculator
Building stairs that are comfortable and code-compliant requires precise measurements. This calculator determines the number of steps, individual riser height, and stringer length from your total rise and desired run.
Enter Your Measurements
Results
How to Use This Calculator
- Measure the total rise from the finished floor at the bottom to the finished floor at the top, in inches.
- Enter your desired tread depth (10 inches is standard).
- Enter your target riser height (7–7.75 inches meets most codes).
- Review the calculated dimensions.
How Stairs Calculation Works
Building codes require consistent riser heights — all risers must be within 3/8 inch of each other. This calculator divides the total rise into equal risers as close to your target height as possible. The stringer length is the diagonal measurement needed to cut your stair stringers (typically 2×12 lumber). IRC residential code requires: maximum riser height of 7.75 inches, minimum tread depth of 10 inches, and minimum stair width of 36 inches.
Formula
Risers = round(Total Rise ÷ Desired Riser Height). Actual riser = Total Rise ÷ Risers. Treads = Risers - 1. Total run = Treads × Tread Depth. Stringer = √(Total Rise² + Total Run²).