Staircase Riser Calculator Formula
Understand the math behind the staircase riser calculator. Each variable explained with a worked example.
Formulas Used
Number of Risers
risers = round(total_rise / target_riser)Actual Riser Height
actual_riser_height = total_rise / round(total_rise / target_riser)Number of Treads
num_treads = round(total_rise / target_riser) - 1Total Horizontal Run
total_run = (round(total_rise / target_riser) - 1) * tread_depthRiser + Tread Sum
rule_check = total_rise / round(total_rise / target_riser) + tread_depthVariables
| Variable | Description | Default |
|---|---|---|
total_rise | Total Rise (Floor to Floor)(inches) | 108 |
target_riser | Target Riser Height(inches) | 7.5 |
tread_depth | Tread Depth(inches) | 10 |
num_risers | Derived value= round(total_rise / target_riser) | calculated |
How It Works
How to Calculate Stair Risers
Formula
Number of Risers = round(Total Rise / Target Riser Height)
Actual Riser Height = Total Rise / Number of Risers
Number of Treads = Risers - 1
The International Residential Code limits risers to a maximum of 7-3/4 inches and requires a minimum tread depth of 10 inches. A common comfort rule is that riser + tread should equal 17 to 18 inches.
Worked Example
A floor-to-floor height of 108 inches (9 feet) with a 7.5-inch target riser and 10-inch treads.
total_rise = 108target_riser = 7.5tread_depth = 10
- 01Number of risers = round(108 / 7.5) = round(14.4) = 14 risers
- 02Actual riser height = 108 / 14 = 7.714 inches
- 03Number of treads = 14 - 1 = 13 treads
- 04Total run = 13 x 10 = 130 inches (10 ft 10 in)
- 05Comfort check: 7.714 + 10 = 17.71 in (within the 17-18 range)
Ready to run the numbers?
Open Staircase Riser Calculator