Calculate stair dimensions including number of steps, actual riser height, total horizontal run and stringer length. Enter your total rise and preferred riser height to get a complete stair layout that meets building code requirements.
Common presets:
Enter total rise to calculate steps.
The number of steps is the total rise divided by the riser height:
Steps = Round(Total Rise ÷ Riser Height)
The actual riser height is adjusted so all steps are equal:
Actual Rise = Total Rise ÷ Number of Steps
Stringer length is calculated using the Pythagorean theorem:
Stringer = √(Total Rise² + Total Run²)
Always verify requirements with your local building authority — some jurisdictions are stricter than IRC minimums.
Code compliance is a minimum — comfortable stairs go a step further. The classic ergonomic formula for residential stairs is:
2 × Riser + Tread = 24–25 inches
An 8-ft floor-to-floor height is 96 inches. Using a 7-inch riser: 96 ÷ 7 = 13.7 — round to 14 risers. Actual riser = 96 ÷ 14 = 6.86 inches. With 11-inch treads, total run = 13 treads × 11 = 143 inches (11.9 ft) of horizontal space needed.
Stair stringers are typically cut from 2×12 lumber (1.5×11.25 in actual). The minimum net section (solid wood remaining after notching) must be at least 3.5 inches at every cut point to maintain structural strength.
In most jurisdictions, yes. New stairs in existing homes require a permit in most US states. Replacement of existing stairs in-kind sometimes does not, but always check with your local building department before starting.