Staircase design basics
Building a safe, code-compliant staircase requires precise measurements. The number of steps, height of each riser, and depth of each tread must all work together. This calculator takes your total floor-to-floor height and desired step proportions, then determines how many steps you need and what their actual dimensions will be.
How the calculation works
The calculator uses your total rise (the vertical distance from bottom to top floor) and your target riser height to determine the number of steps required. It then calculates the actual riser height by dividing the total rise evenly among all steps. The total run—the horizontal distance the staircase spans—is computed by multiplying the number of treads by the tread depth.
Number of steps = ceil(Total rise ÷ Target riser height) and Actual riser = Total rise ÷ Number of steps
The formula
Total run = (Number of steps − 1) × Tread depth
Note: You use one fewer tread than steps because the top landing counts as the final step.
Worked example
Imagine you're building a staircase between two floors that are 120 inches apart (10 feet). You want each step to be roughly 7.5 inches high, and you plan treads 10 inches deep.
Step 1: Calculate number of steps
- Total rise = 120 inches
- Target riser = 7.5 inches
- Number of steps = 120 ÷ 7.5 = 16 steps
Step 2: Find the actual riser height
- Actual riser = 120 ÷ 16 = 7.5 inches (in this case, it divides perfectly)
Step 3: Calculate total run
- Number of treads = 16 − 1 = 15
- Total run = 15 × 10 = 150 inches (12.5 feet)
So your staircase will have 16 steps, each 7.5 inches high and 10 inches deep, spanning 150 inches horizontally.
What if it doesn't divide evenly?
Suppose the total rise were 119 inches instead:
- 119 ÷ 7.5 = 15.87, which rounds up to 16 steps
- Actual riser = 119 ÷ 16 = 7.4375 inches per step
The calculator adjusts all risers equally to fit your space. This tiny variation is invisible in practice but ensures every step is identical—a critical safety feature.
Tips for accurate stair planning
Measure twice. Total rise must include finished flooring on both levels. If you're building on a concrete slab that will receive tile, add that thickness to your measurement.
Check local codes first. Before designing, confirm your area's riser and tread requirements. Some jurisdictions mandate minimum tread depth (often 10 inches) or maximum riser height (often 7.75 inches for residential). Commercial buildings have stricter rules.
Plan the landing. The calculator shows horizontal run, but account for the landing at the top and any intermediate landings. A landing counts as one step in terms of vertical rise but adds to your total horizontal distance.
Test the math on paper. Once you have your step count and dimensions, multiply them back: (Number of steps × Riser height) should equal your total rise. (Number of treads × Tread depth) should equal your total run. This confirms the design before you build.
This calculator provides an estimate to guide your design—always verify measurements on-site and consult building codes or a professional before construction.