Last updated: 2026-06-16

Rise, Run, and the Parts of a Step

A staircase is described by two overall measurements and two per-step measurements. The total rise is the vertical height from one finished floor to the next. The total run is the horizontal distance the flight covers along the floor. Each step is built from a riser, the vertical face, and a tread or going, the horizontal surface that is stepped on. The number of treads is one fewer than the number of risers, because the top riser lands on the upper floor itself rather than on a separate tread.

Why Every Step Must Be Equal

A flight is laid out so that all risers are the same height and all treads the same depth. The eye and foot learn the rhythm of a stair within the first one or two steps, so a single odd riser becomes a trip hazard. For that reason the target riser is treated as a goal: the calculator divides the total rise by it, rounds to a whole number of steps, then recomputes the exact riser height that divides the rise evenly.

The 2R + T Comfort Rule

Stair comfort is commonly checked with the two-risers-plus-one-tread rule. Twice the riser height $R$ plus the tread depth $T$ should fall close to 63 cm:

A result well below this gives shallow, cramped steps; well above it gives a steep, tiring climb.

Worked Example

For a 280 cm rise with an 18 cm target riser and a 28 cm tread, the number of steps, actual riser, and comfort value are:

The comfort value of 63 cm sits squarely in the comfortable band.

Local building codes set the legal minimum and maximum riser height, tread depth, headroom, and handrail requirements, and these differ between jurisdictions. Verify any design against the rules that apply where the staircase is built.