Stairs Calculator

Explanation

A comfortable staircase must follow the **Blondel Formula** (or Step Rule). If ignored, the stairs will be tiring or dangerous (trip hazard). ### The Rule **2R + T = 24 to 25 inches (60-64 cm)** - **R** (Rise): Height of the step. Ideally 7 inches (17-18 cm). - **T** (Tread/Run): Depth of the step. Ideally 10-11 inches (25-28 cm). ### Calculation 1. Measure total rise (floor to floor). 2. Divide by ideal rise (7") to get number of steps. 3. Adjust to get a whole number. 4. Calculate required tread using the formula. ### Total Run This is the horizontal distance the stairs cover. Total Run = (Number of steps - 1) x Tread.

Examples

• Total rise 9ft (108"). 15 steps of 7.2". Tread 10.6". (2x7.2 + 10.6 = 25" -> Perfect).
• If tread is too short (<9"), it becomes a steep ladder/ladder stairs.

FAQ