Staircase steps calculator

How it works

We aim for a comfortable riser around 17-18 cm: the number of steps is the total height divided by this value. The tread comes from the «step rule» (2×riser + tread ≈ 63 cm).

Note

This is a rough estimate: for code-compliant stairs check local regulations and, for structural work, a professional.

Where the pace rule comes from

The formula «two rises plus one going equals sixty-three centimetres» comes from the French architect François Blondel, who in the seventeenth century derived it from the average human pace on the flat, about sixty-three centimetres, and from the fact that climbing costs twice as much as walking. It is not a historical quirk: it is why a staircase that respects that sum is climbed without thinking, and one that does not tires you or trips you.

The range used today is between 62 and 64 centimetres. Below it, steps become wide and shallow and force a shuffling gait; above it, the climb becomes hard work and on the way down the foot finds no support.

The number of rises comes first

You always start from the total height from finished floor to finished floor, that is including the coverings and the thickness of the slab, and divide it by a desired rise of 17 to 18 centimetres. The result is almost never a whole number, so you round to the nearest number of steps and recalculate the rise by dividing the height by that number: it is the rise that has to adapt, not the height.

The rule that admits no exception is that every rise in a flight must be identical to the others. A step even one centimetre higher or lower than the rest is the number one cause of falls at home, because the foot climbs from habit and does not look. There is always one going fewer than the rises, because the last rise lands directly on the upper floor.

The dimensions that make a staircase safe

The headroom over your head, measured vertically from the nosing of each step, should not fall below two metres: it is the constraint that most often forces a loft staircase to be redesigned. The usable width of an internal domestic stair starts at eighty centimetres, and below ninety it becomes hard to get furniture past.

Then the balustrade, which in buildings must be at least a metre high and must not be climbable by a child, with openings under ten centimetres. And the handrail, the most useful element of all, which should extend beyond the first and last step: that is where the hand looks for support exactly as the stair runs out.

Stairs that are not straight flights

In spiral stairs and winders the going changes along the step, and the pace rule applies to the walking line, that is along the path actually taken when climbing, about fifty centimetres from the inner edge. Near the newel the step is too narrow to put a foot on, which is why a spiral of small diameter is uncomfortable by definition.

If the staircase is structural work or habitability is involved, the minimum dimensions are set by local building regulations and fire rules, which differ from place to place and between private and public buildings. This page is for designing the proportion, not for replacing that check.

Nearby tools

For the gradient of a ramp there is Slope calculator. For room dimensions Room area and volume and Areas and perimeters.