What Is the Rise & Run Calculator?
Find the optimal riser height and tread depth combination for any total rise using the industry-standard 2R+T comfort rule. This optimizer evaluates every valid step count within your specified range and ranks combinations by how closely they approach the ideal 2R+T = 25 inches.
How to Use This Calculator
- Enter your total floor-to-floor rise.
- Set the minimum and maximum number of steps to consider.
- Review the ranked combinations - the top result is the most comfortable.
- Use the best riser and tread dimensions in your stair design.
Why Accurate Rise & Run Calculations Matter
The 2R+T rule (two risers plus one tread depth ≈ 24–25 inches) has been the gold standard for stair comfort since François Blondel published it in 1672. Stairs that deviate significantly from this ratio feel either uncomfortably steep or annoyingly shallow. Our optimizer finds the combination closest to the ideal for your specific total rise.
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Frequently Asked Questions
What is the 2R+T rule?+
The 2R+T rule states that two times the riser height plus the tread depth should equal 24 to 25 inches. For example: 2 × 7.25" + 10.5" = 25". This formula produces the most comfortable stride on stairs.
Who invented the 2R+T rule?+
François Blondel, a French architect, published this rule in his 1672 work 'Cours d'architecture.' He based it on observations of the natural stride length when climbing.