Stair Calculator
Use our Stair Calculator for precise calculations to ensure a safe and comfortable staircase design that meets building codes.
Stair Calculator — Overview
The Stair Calculator helps architects, builders, and homeowners determine the appropriate number of risers (steps) and the adjusted rise per step for a staircase. You provide the total vertical rise (floor-to-floor height) in meters and the preferred run and rise per step in centimeters. The tool calculates the number of steps required and adjusts the rise per step so that the total rise is evenly distributed.
This calculator uses the ergonomic approach of rounding the number of risers up so that the total rise is fully covered, then computes an adjusted rise value to keep steps uniform. It also computes the total horizontal run of the staircase based on the chosen run per step, ensuring that the design meets not just aesthetic but also functional design standards.
How it Works
Steps to calculate your staircase dimensions:
- Convert the desired rise per step from centimeters to meters.
- Divide the total rise by the rise per step to get the raw number of steps.
- Round the number of steps up (Math.ceil) to ensure the total rise is covered.
- Compute the adjusted rise per step by dividing the total rise by the final step count.
- Compute the total run by multiplying the number of steps by the run per step.
Adjusted Rise (m) = Total Rise (m) / Number of StepsExample
Suppose you have a total rise of 3.0 m, a desired run per step of 30 cm, and a desired rise per step of 18 cm.
Convert the desired rise to meters: 18 cm = 0.18 m. Raw number of steps = 3.0 / 0.18 ≈ 16.67. Rounding up gives 17 steps. Adjusted rise = 3.0 / 17 ≈ 0.1765 m → 17.65 cm. Total run = 17 × 30 cm = 510 cm = 5.10 m.
Tip: Most building codes and comfortable stair design recommend a rise between 14 cm and 20 cm and a run (tread depth) typically between 25 cm and 30 cm. Always check local building codes before finalizing designs to ensure safety and compliance.
Frequently Asked Questions
What if the adjusted rise is too high or too low?
If the adjusted rise falls outside your comfort or code range, adjust the desired rise per step or the run per step and re-run the calculation. Increasing the number of steps (smaller rise) or changing tread depth can improve comfort and compliance. This ensures that the overall stair design adheres to safety standards.
Should I always round up the number of steps?
Yes. Rounding up ensures the entire vertical distance is covered without shortfall. After rounding up, the calculator computes an adjusted uniform rise so that the total rise is exact and comfortable for use.
Does this include landings or headroom checks?
No. This calculator focuses on riser and run calculations only. For full stair design, including landings, headroom, and handrails, consult building codes and a licensed architect or engineer to ensure compliance and user safety.
What is the best height and run for stairs?
The ideal stairs should have a rise typically between 14 cm to 20 cm, and a run (tread depth) of approximately 25 cm to 30 cm. These measurements contribute to a comfortable and safe climbing experience.
Further Reading
For comfortable stair design, consider the formula by Blondel (2 × rise + run ≈ 63 cm) as a quick ergonomic check and always validate against local codes. Additionally, explore resources on best practices for stair design.