Staircase Set-Out Calculator

How the staircase set-out calculator works

Enter the floor-to-floor rise (the finished vertical height between the two floors), the largest riser you are willing to use, and the tread going. The calculator divides the rise by your maximum riser and rounds up to a whole number of risers, so no single step is taller than your limit. It then divides the total rise equally across those risers to give the exact riser height, and works out the going, total horizontal run, straight-line stringer length and the pitch angle.

Risers, treads and the going

A straight flight has one more riser than it has treads: the final riser lands on the upper floor. The going is the horizontal depth of each tread measured from one riser face to the next, not including any nosing overhang. Total run is the going multiplied by the number of treads, and the stringer length is the diagonal that spans the whole flight — the minimum board length before you cut the housings.

Getting a comfortable pitch

The 2R + G figure (twice the riser plus the going) is a well-established rule of thumb for comfortable stepping. A shallower pitch with a bigger going and smaller riser is easier to climb but takes more floor space; a steeper pitch saves space but is harder to use. The calculator shows the pitch angle so you can judge the trade-off, and the 2R + G value so you can sanity-check comfort.

Set-out on site

Use the individual riser height to mark a storey rod, and the going to mark the treads along the stringer. Transfer the riser and going to a framing square with stair gauges to scribe each housing. Cut a trial stringer first and offer it up before batch-cutting — small errors in the floor-to-floor measurement multiply across the flight.

Regulations and safety

This tool sets out geometry only. Riser height, going, maximum pitch and headroom are all controlled by the Building Regulations that apply to your project (for example Approved Document K in England), and limits differ between private, common and public stairs. Always confirm your finished flight against the current regulations and, for any load-bearing element, a suitably qualified professional.

Using this alongside other BuildMetricLab tools

Pair the set-out with our concrete steps, floor joist and timber calculators when you are planning an opening and its trimming. Every BuildMetricLab tool runs entirely in your browser — no sign-up, nothing sent anywhere, and every formula shown so you can audit the maths.