Stair Riser Height vs. Tread Depth: Getting the Ratio Right
Why riser height and tread depth trade off against each other, the rule of thumb builders use to balance them, and what building code requires.
Riser height and tread depth aren't independent choices — taller risers need shallower treads to feel natural underfoot, and shorter risers can support deeper treads. Get the balance wrong and stairs feel awkward even when each measurement is individually code-compliant.
The rule of thumb
A widely used builder's guideline is: 2 × riser height + tread depth should land between 24 and 25 inches. A 7-inch riser paired with a 10.5-inch tread (2×7 + 10.5 = 24.5) hits that target comfortably.
What code actually requires
| Element | Typical IRC limit |
|---|---|
| Maximum riser height | 7¾" (196 mm) |
| Minimum tread depth | 10" (254 mm) |
| Riser variance within a flight | ⅜" (9.5 mm) max |
Code sets outer limits, not a comfort target — a staircase built right at the 7¾" riser maximum with exactly a 10" tread is legal almost everywhere but feels noticeably steeper than one built around the 24-25 inch rule of thumb.
Enter a target riser height and tread depth into the Stair Calculator to see the actual angle and code-compliance check for your specific combination.