Stair Calculator
⚙️ Input Values
Total vertical height the staircase must climb
Recommended minimum: 10"
📊 Result
📐 Live Stair Diagram
Updates after calculation
📋 Calculation History
📖 About the Stair Calculator
Calculating stairs correctly is critical for safety and building code compliance. The two main measurements are rise (vertical height of each step) and run (horizontal depth of each tread). Most building codes require a maximum rise of 7.75 inches (196mm) and a minimum run of 10 inches (254mm).
The formula for stringer length uses the Pythagorean theorem: √(total rise² + total run²). This gives you the diagonal cut length of your stringer boards. For exterior stairs, use pressure-treated lumber rated for ground contact.
Our stair calculator handles all the math automatically. Enter the total height between floors and your preferred step height, and the tool calculates the optimal number of steps, individual rise and run dimensions, total stringer length, and stair angle. A visual diagram shows the proportions of your staircase to help you visualize the result before you cut.