Stair Riser Height & Building Code
Quick answer: the standard riser is about 7.5 in, with a code maximum around 8.25 in and a minimum tread of 10 in. Divide total rise by your target riser, then even out the result for a safe flight.
- Riser height rules
- Tread depth
- How to calculate
- Riser chart
- Common mistakes
Riser height rules
The IRC allows risers between 4 and 8.25 inches, and the sweet spot for comfortable, code-safe stairs is around 7.5 inches. Two rules matter most: keep every riser in a flight within 3/8 in of the others, and don't exceed the max. Inconsistent risers are the #1 trip hazard and a frequent inspection fail.
Tread depth
Tread depth is measured from nosing to nosing. Code requires a minimum of 10 in (IRC) for residential stairs; 11 in is more comfortable. A common formula pairing: riser + tread ≈ 17–18 in (e.g., 7.5 + 10.5 = 18). Match the riser to the tread so the flight feels natural to climb.
How to calculate
Measure the total rise — the vertical distance from finished floor to finished floor. Divide by your target riser (7.5 in) and round up to get the number of risers, then divide the total rise by that number for the exact riser. The number of treads is risers minus one (the top riser meets the landing).
Riser chart
| Total rise | Risers @7.5 in | Exact riser | Treads |
|---|---|---|---|
| 90 in | 12 | 7.5 in | 11 |
| 105 in | 14 | 7.5 in | 13 |
| 120 in | 16 | 7.5 in | 15 |
| 144 in | 19 | 7.6 in | 18 |
If the exact riser lands above 8.25 in, add a riser to the flight instead.
Worked example
A 105-in rise between two floors:
- Target risers: 105 ÷ 7.5 = 14 → 14 risers
- Exact riser: 105 ÷ 14 = 7.5 in
- Treads: 14 − 1 = 13 at ~10.5 in each
The stairs calculator turns this into stringer length and material counts.
Common mistakes
- Uneven risers. Keep all within 3/8 in of each other.
- Oversized risers. Over 8.25 in fails code.
- Shallow treads. Under 10 in is a safety issue.
- Rounding up but not evening out. Always redistribute the last riser.
FAQ
The standard riser height is about 7.5 inches. Most building codes allow risers between 4 and 8 inches, with the maximum 8.25 inches under the IRC, and all risers in a flight within 3/8 inch of each other.
Standard tread depth is about 10-11 inches, measured from nosing to nosing. Building codes require a minimum tread depth of 9-10 inches depending on the code.
Divide the total rise (floor to floor) by your target riser height, round up to get the number of risers, then divide the total rise by that count. For a 105-inch rise at 7.5 inches, you get 14 risers at exactly 7.5 inches each.
All risers in a single flight must be within 3/8 inch of each other. Inconsistent risers are a trip hazard and a common code violation — always even out the last riser rather than leaving one shorter.