The 7–11 rule and the comfort formula
A rise near 7 inches with a tread of 11 inches is the everyday sweet spot: 2(7) + 11 = 25. The rule tracks a natural stride, so stairs built to it feel even and safe. Every step in a flight must share the same rise — that is the part people get wrong.
Sizing a flight from the total rise
Start from the floor-to-floor height, pick the number of risers, and the geometry follows. Treads are always one fewer than risers, since the top floor is the last landing.
- Risers. Total rise ÷ target rise (~7 in), rounded to a whole number.
- Actual rise. Total rise ÷ number of risers — this is what you build to.
- Treads. Number of risers minus 1.
- Total run. Number of treads × tread depth — the floor space the stairs eat up.
US code limits (IRC / IBC)
| Dimension | Min | Max | Typical home |
|---|---|---|---|
| Riser (rise) | 4 in | 7.75 in | 7 to 7.5 in |
| Tread (run) | 10 in | — | 10 to 11 in |
| Stair width | 36 in | — | 36 in (44 for two people) |
| Nosing overhang | 0.75 in | 1.25 in | 1 in |
| Headroom | 80 in | — | 80 in clear |
Any two risers in the same flight may differ by no more than 3/8 inch. Uneven steps are a leading cause of falls, because your body expects every step to be the same after the first one. A comfortable pitch lands between 30° and 38°.
Common questions
What is the difference between rise and run?
Rise is the vertical height of one step; run is the horizontal depth you place your foot on (also called the tread). US code allows a rise up to 7.75 inches and requires a run of at least 10 inches. Together they set how steep and how comfortable the stairs feel.
Why is 2R + R the rule for comfortable stairs?
Two times the rise plus the run should land between 24 and 25 inches, which matches the length of a natural walking stride. A 7-inch rise with an 11-inch run gives 2(7) + 11 = 25, close to ideal. Adding an inch to the rise means taking an inch off the run.
How many steps do I need for a given height?
Divide the total floor-to-floor height by a target rise near 7 inches and round up to a whole number of risers, then divide the height by that count to get the exact rise. For a 108-inch rise: 108 / 7 is about 15.4, round to 15 risers, so each rise is 7.2 inches.
