Stair Calculator
Calculate stair dimensions and number of steps
Enter Stair Dimensions
Vertical height from floor to floor
Between 4 and 7.75 inches (typically 6-7.5)
Typically 10-11 inches
Stair Calculation Result
About This Calculator
The Stair Calculator helps you calculate stair dimensions, number of steps, rise, run, and stringer length for building stairs. It's essential for construction projects, remodeling, and ensuring stairs meet building code requirements.
This tool is useful for contractors, carpenters, architects, and DIY enthusiasts planning stair construction. The calculator helps ensure stairs are safe, comfortable, and compliant with building codes by calculating optimal rise and run dimensions.
Formula & Calculation Method
Stair calculations use the following formulas:
- Number of Steps: Total Rise / Desired Rise per Step (rounded up)
- Actual Rise per Step: Total Rise / Number of Steps
- Total Run: (Number of Steps - 1) × Run per Step
- Stringer Length: √(Total Rise² + Total Run²)
- Angle: arctan(Total Rise / Total Run) × (180 / π)
- Building Code Check: 2R + T = 24-25 inches (where R = rise, T = run)
Where:
- Rise = vertical height of each step
- Run = horizontal depth of each step (tread depth)
- Total Rise = total vertical height from floor to floor
- Stringer = diagonal support board that holds the steps
Building Code: Most building codes require 2R + T to be between 24 and 25 inches for safety and comfort. Typical rise is 6-8 inches, and typical run is 10-11 inches.
How to Use This Calculator
Frequently Asked Questions
What is the standard rise and run for stairs?
Standard residential stairs typically have a rise of 7-7.5 inches and a run of 10-11 inches. Commercial stairs may have different requirements. Always check local building codes.
What is the building code requirement for stairs?
Most building codes require that 2R + T (twice the rise plus the run) equals 24-25 inches. This formula ensures stairs are safe and comfortable to use. Individual rise should be between 4-7.75 inches, and run should be at least 10 inches.
What is a stringer?
A stringer is the diagonal support board that holds the steps (treads and risers) of a staircase. Stringers are typically cut from 2×12 lumber and run along the sides of the stairs.
How do I calculate the number of steps needed?
Divide the total rise (floor to floor height) by the desired rise per step. Round up to get the number of steps. Then divide the total rise by the number of steps to get the actual rise per step, which ensures all steps are uniform.
Calculator by
NumCalculators Editorial Team
Multi-disciplinary Expert Team