Metric Stair Calculator

Short answer

Divide the total rise by your target riser height and round to a whole number of risers. Then divide the total rise by that number for the exact riser height. A straight stair has one fewer tread than risers, so total run is treads times tread run. For 2,700 mm of rise and a 180 mm target, that is 15 risers of 180 mm and 14 treads.

Total rise (floor to floor) (mm)Target riser height (mm)Tread run (mm)

Number of risers: 15
Exact riser height: 180 mm
Number of treads: 14
Total run: 3,570 mm

Formula

Risers = round(Total rise ÷ Target riser) · Riser = Total rise ÷ Risers · Run = (Risers − 1) × Tread

Worked example

2,700 mm total rise ÷ 180 mm = 15 risers of exactly 180 mm. 14 treads × 255 mm = 3,570 mm total run.

Before you rely on it

Maximum riser height, minimum run and uniformity tolerances are set by Part 9 of the building code your province has adopted. Check them before you cut stringers.

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