Stair Rise and Run Calculator
Calculate the individual rise height of each stair step given your total floor-to-floor height and number of steps. Use it when designing or building a staircase to ensure safety and code compliance.
About this calculator
A comfortable, safe staircase depends on the relationship between riser height (rise) and tread depth (run). The rise is the vertical height of each step, calculated by dividing the total floor-to-floor height by the number of steps: Rise per Step = Total Rise / Number of Steps. Building codes (IRC) typically limit riser height to a maximum of 7¾ inches and a minimum of 4 inches, while tread depth must be at least 10 inches. A widely used comfort rule is: 2 × Rise + Run = 24 to 25 inches. Consistent riser heights are critical — even a ¼-inch variation between steps can cause trips and falls. The number of steps is often determined by dividing the total rise by a target riser height and rounding to the nearest whole number.
How to use
Suppose your floor-to-floor height is 108 inches and you want to use 14 steps. Apply the formula: Rise per Step = 108 / 14 = 7.71 inches per step. Check against code: 7.71 inches is under the 7¾-inch maximum — this passes. Using the comfort rule with a 10-inch tread: 2 × 7.71 + 10 = 25.43 inches, which falls within the comfortable 24–25.5 inch range. This confirms that 14 steps with a 10-inch tread depth produces a safe, comfortable staircase for your project.
Frequently asked questions
What is the maximum allowable riser height for residential stairs according to building code?
The International Residential Code (IRC) sets a maximum riser height of 7¾ inches (196 mm) for residential staircases. The minimum riser height allowed is 4 inches to prevent people from catching their feet under a step. All risers within a single staircase must be within 3/8 inch of each other to ensure consistent stepping rhythm and reduce trip hazards. Local jurisdictions may adopt stricter limits, so always verify with your local building department before finalizing your stair design.
How do I determine the right number of steps for my staircase?
Start with your total rise (floor-to-floor height in inches) and divide by your desired riser height — typically 7 to 7¾ inches for comfort. Round the result to the nearest whole number to get your step count, then recalculate the exact riser height by dividing total rise by that number of steps. For example, a 102-inch rise divided by a target of 7 inches gives 14.57 steps, rounded to 15, yielding a riser of 102/15 = 6.8 inches. Iterating this way keeps all risers equal and code-compliant.
Why is consistent riser height so important for stair safety?
Humans develop an unconscious gait pattern when climbing stairs, expecting each step to feel the same height as the previous one. Research and building codes recognize that a variation of more than 3/8 inch between the tallest and shortest riser in a flight significantly increases trip-and-fall risk, particularly on the way down when visibility is limited. Inconsistent rises often result from measurement errors or settling of the subfloor, so careful framing and a final check with a level are essential. Even a single anomalous step can cause a serious fall for elderly or visually impaired users.