Comfortable, safe stairs come down to two numbers staying in balance: how tall each step is, and how deep it is.
The two measurements that matter
- Riser height — the vertical height of a single step.
- Tread depth — the horizontal depth of a single step, where your foot lands.
Most residential building codes cap riser height around 7 3/4” maximum and require tread depth of at least 10”. Stairs outside these ranges tend to feel cramped or unexpectedly steep, and can fail inspection.
Dividing an awkward total rise evenly
Total rise (the full floor-to-floor height) rarely divides evenly into a round riser height. The standard approach: pick a target riser height (commonly around 7”–7.5”), divide the total rise by that target, and round to the nearest whole number of risers. Then divide the total rise by that whole number to get the exact, evenly-spaced riser height for every step.
For example, a total rise of 108” divided by a 7.5” target suggests roughly 14.4 risers — round to 14, then 108” ÷ 14 = 7.71” per riser, comfortably under the 7 3/4” limit.
The 2R + T comfort rule
A widely used rule of thumb for stair comfort is:
2 × Riser height + Tread depth = 24 to 25 inches
Stairs that fall within this range tend to feel natural to walk. Falling well outside it usually means the stairs will feel either too steep (small tread, tall riser) or awkwardly shallow (large tread, short riser).
Letting the numbers do the work
Getting riser count, riser height, tread depth, and the comfort check right by hand means juggling several interdependent numbers at once. Our Stair Rise & Run Calculator takes your total rise, available run, and target riser height, then returns the number of risers and treads, the exact riser height and tread depth, the resulting stair angle, and whether your numbers fall inside typical code limits.
Always confirm locally
Building codes vary by region and by stair type (interior, exterior, spiral, etc.). Treat these ranges as a strong starting point, not a substitute for checking your local code before finalizing a stair design.