The following is a rule-of-thumb formula for interior stairs, as specified in the Architectural Graphic Standards.
- Riser + Tread = 17.5 inches: 7.5 inches for the riser height; 10 inches for the tread depth.
- Riser * Tread = 75 inches.
- 2(Riser) + Tread is greater than or equal to 24 inches (minimum threshold) or less than or equal to 25 inches (maximum threshold).