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Stair Calculator

Plan a staircase from the total rise.

How it is calculated

The total rise is the vertical distance from the finished floor below to the finished floor above, in millimetres. The tool divides it by your ideal riser height and rounds to the nearest whole number of steps: steps = round(rise / ideal), with a minimum of 1. The actual riser is then rise / steps, so every step is identical and the total is exact.

If the ideal height is left empty or is not positive, 175 mm is used. Rise and ideal must be in the same unit (mm). Only the riser height is calculated; the tread depth, headroom and the local building code limits are not checked, so confirm them separately.

Worked example

Total rise 2700 mm, ideal riser 175 mm. 2700 / 175 = 15.43, rounded to 15 steps. Actual riser = 2700 / 15 = 180 mm. The tool shows 15 steps and a riser of 180.00 mm. Note that 15 risers is the count of vertical rises; the number of treads is usually one fewer when the top floor acts as the last tread.

Try this example →

Common mistakes

  • Measuring the rise to the unfinished floor instead of the finished floors; flooring thickness changes the rise.
  • Entering metres or inches: the fields expect millimetres, so 2.7 would produce one step.
  • Assuming the actual riser equals the ideal one; it is the ideal adjusted so a whole number of steps fits.
  • Counting the number of treads as the number of steps given; with the top floor as the last tread there is one fewer tread than risers.

About this calculator

This calculator plans a staircase by dividing the total rise (floor-to-floor height) by a maximum comfortable riser height — commonly capped around 7 inches (178 mm) under residential building codes — rounding up to a whole number of steps, then recomputing the actual riser height = total rise ÷ number of steps so every riser comes out identical. Most codes require riser heights to be uniform within about ⅜ inch (10 mm) throughout a flight, since inconsistent risers are a leading cause of stair-related trips and falls.

Carpenters, general contractors, and DIY builders use this calculation before cutting a single stringer, and architects use it early in a floor plan to confirm a staircase will fit within the available floor-to-floor height and horizontal run while staying code-compliant. Enter the total rise to get the step count and exact riser height.

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