What a 6.5-inch riser paired with a 11-inch tread actually gives you — pitch, comfort, and code status — plus the calculator to size a full flight.
A 6.5-inch riser with a 11-inch tread is compliant under IRC 2021 (max riser 7.75″, min tread 10.0″), and compliant under the IBC commercial standard (max riser 7.0″, min tread 11.0″).
This pair is one step's geometry. To size a complete flight for your floor-to-floor height, enter your total rise in the calculator and it will hold the riser near 6.5″ while checking every code limit.
A 6.5-inch riser with a 11-inch tread produces a 30.6-degree pitch, which is one of the more relaxed pairings for a staircase. In practice that means it is easy to climb and descend, friendly for children and older users, but it consumes the most horizontal run. Its Blondel value of 24.0 inches lands right in the 24–25 inch Blondel comfort band, so it should feel natural underfoot.
Across a typical flight of about 14 treads, the 11-inch tread depth works out to roughly 11.9 feet of horizontal run — a moderate footprint. This pairing clears both the residential IRC and the stricter commercial IBC, which makes it unusually versatile — usable in a home or a light-commercial setting without redesign.
Pick this pairing when comfort and easy access matter more than saving floor area — it is a good main-stair choice in a home with the space to accommodate the longer run. Whatever your floor-to-floor height, the calculator below will hold the riser near 6.5 inches, divide the rise into uniform steps, and check the result against the code you select.