Stair Calculator
NEWCalculate stair dimensions including number of steps, rise per step, run per step, total run, stringer length, and stair angle. Includes IRC building code validation.
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How to use Stair Calculator
- Enter the total rise (floor-to-floor height) and desired run per step.
- Add tread thickness and nosing overhang if applicable.
- Click Calculate to see step count, dimensions, angle, and building code validation.
What is Stair Calculator?
A stair calculator determines the optimal number of steps, rise, and run for a staircase based on the total floor-to-floor height. It applies building code rules (IRC) and the 2R+T comfort rule to ensure safe, comfortable stairs.
This calculator warns you if riser heights exceed 7.75 inches (IRC maximum), if the run is too short, or if the 2R+T comfort rule falls outside the ideal 24-25 inch range. It also calculates the stringer board length you need to cut.
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FAQ
- What is the standard stair rise and run?
- Standard residential stairs have a 7-7.75 inch riser height and 10-11 inch tread depth. The IRC maximum riser is 7.75 inches and minimum tread is 10 inches.
- What is the 2R+T rule?
- The comfort rule states that 2 times the riser height plus the tread depth should equal 24-25 inches. This formula helps determine comfortable stair proportions.
- How do I calculate stringer length?
- Stringer length = square root of (total rise squared + total run squared). This is the diagonal length of the stair from top to bottom.
- What is the maximum stair angle allowed?
- Residential stairs should not exceed 38 degrees. Commercial stairs are typically limited to 32-33 degrees.
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