Staircase Calculator

How it is calculated

Enter the total rise (floor-to-floor height) and the riser height you would like, both in centimetres. The tool divides them and rounds to the nearest whole number of steps: steps = round(total rise / target riser), never fewer than 1. Because steps must be whole, it then recalculates the riser that makes them all equal: actual riser = total rise / steps, shown to one decimal.

A comfortable stair has equal risers, so the actual riser is the value to cut or build to. It will usually differ slightly from your target. The tool covers rise only. Tread depth, headroom, total run and local building-code limits on riser and tread size are not calculated, so check them separately. The count is the number of risers, which is one more than the number of treads when the top step is the upper floor.

Common mistakes

• Entering the rise in metres or inches. Both values must be in centimetres.
• Using the target riser as the real riser. After rounding, the actual riser is the one to build.
• Measuring the rise before the final floor finish is known; thick flooring on top changes the total rise.
• Forgetting that a flight with N risers has N − 1 treads when the upper floor acts as the last tread, then miscounting boards.