How to Work Out a Staircase: Rise, Going and Pitch (UK Guide)

Everything begins with the total rise, the vertical distance from the finished floor you step off to the finished floor you land on. Not the ceiling height, and not the joist-to-joist gap. Measure it in millimetres, and measure it plumb, because a stair that is set out from a height that is 30 mm wrong will be wrong on every single step. In a typical UK two-storey home this height is somewhere between 2,500 and 2,900 mm once floor finishes are allowed for.

Takeaway: measure finished floor to finished floor in millimetres before anything else; every other number is derived from it.

Divide the total rise by an ideal step height of around 190 mm and round to the nearest whole number. That gives the number of risers. The individual rise is then the total rise divided by that number of risers. Say your height is 2,600 mm: 2,600 divided by 190 is 13.7, which rounds to 14 risers, giving an individual rise of 185.7 mm. The number of treads, called goings, is always one fewer than the risers, because the top floor itself acts as the last "step". So 14 risers means 13 goings.

Takeaway: risers equal total rise divided by about 190 mm, rounded; treads are always one fewer than risers.

The rise is the height of each individual step. The going is the horizontal depth of each tread measured from the front edge of one step to the front edge of the next, which is not the same as the physical tread board, since the nosing overhangs. The pitch is the angle of the whole flight, found from the rise and going together. Under Approved Document K in England and Wales, a private domestic stair allows a rise up to 220 mm, a going of at least 220 mm, and a maximum pitch of 42 degrees. Utility and general access stairs are tighter, capping the rise at 190 mm and 170 mm respectively.

Takeaway: for a home stair, keep the rise at or below 220 mm, the going at or above 220 mm, and the pitch at or below 42 degrees.

The regulations tie rise and going together with a single formula. Twice the rise plus the going must land between 550 mm and 700 mm. This is what stops a staircase feeling like a stepladder or wasting half the hallway. The logic is that steeper steps need shorter treads and shallow steps need deeper ones, so your foot always meets the step the same way. Take the 185.7 mm rise with a 250 mm going: 2 times 185.7 plus 250 is 621 mm, comfortably in the middle of the band. If your figure comes out at 720, the stair is too steep for its tread and you either add a step or deepen the going.

Takeaway: always check 2R plus G falls between 550 and 700 mm; it is the fastest test of whether a stair will feel right.

Take a loft conversion in a Sheffield terrace with a floor-to-floor height of 2,750 mm, a private stair, and a going of 240 mm to save a little space.

Risers: 2,750 divided by 190 is 14.5, rounded to 14 risers. Individual rise: 2,750 divided by 14 is 196.4 mm (within the 220 mm limit). Goings: 14 minus 1 is 13 treads. Pitch: the angle whose tangent is 196.4 over 240 is 39.3 degrees (under 42). Horizontal run: 240 times 13 is 3,120 mm, or 3.12 m. 2R + G: 2 times 196.4 plus 240 is 632.8 mm (inside 550 to 700). Stringer length per side: the diagonal of 2,750 and 3,120 is about 4,160 mm, so 4.16 m.

Every check passes. It is a steeper flight than the ground-floor example because the going was trimmed to 240 mm, but at 39.3 degrees it is still a comfortable, compliant loft stair. You would order the stringer timber at 4.2 m, most likely a planed softwood or engineered stringer from a merchant like Travis Perkins or a local timber yard, and set out the 14 risers from the true floor-to-floor height on site rather than the drawing.

Takeaway: trimming the going makes a stair steeper, not shorter in step count; check the pitch stays under 42 degrees whenever you tighten the going.

Here is where online numbers and real rooms part company. A step count can be perfectly valid and still not fit. The Sheffield example eats 3.12 m of floor in a straight line before you add a landing, and it needs 2,000 mm of headroom measured vertically over the pitch line. Lofts rarely give you a clean 2 m everywhere, which is exactly why Approved Document K allows a reduced headroom for loft conversions, down to 1,900 mm at the centre of the stair and 1,800 mm at the edge. If your opening is too short for the run, the answer is not to crush the going below its limit. It is to switch to a half-landing, add winders, or move the opening. Work out the geometry, then hold it up against the actual space before you commit.

Takeaway: a valid staircase still has to fit; always check the horizontal run and the 2,000 mm headroom against the real opening before cutting timber.

A staircase is more than its steps. You need a handrail on at least one side for a stair under a metre wide, and both sides above that, set 900 to 1,000 mm above the pitch line. Guarding to any drop must not allow a 100 mm sphere through, the classic "no gap a child could get through" test. Landings at the top and bottom must be at least as deep as the stair is wide and kept clear of door swings. None of this changes the step maths, but all of it can change whether the staircase passes building control.

Takeaway: size the steps first, but budget space and height for handrails, guarding and landings before you finalise the layout.

In practice, an experienced stair joiner sets out from the height measured on site on the day, never from the architect's drawing, because floor finishes and joist depths move that number. They will nudge the going by a few millimetres to bring the pitch to something that feels right rather than chasing an exact round number, and they cut the strings from a real diagonal measurement, not the theoretical one, allowing for the newel joints. And they check the headroom by holding a straightedge on the pitch line before the stair is built, because a staircase that fails headroom after it is fitted is an expensive thing to unpick.

Takeaway: set out from the site measurement, tune the going for feel, and prove the headroom before the stair goes in.

Put your floor-to-floor height into the Staircase Calculator (UK) to get the steps, rise, going, pitch and stringer length in one go, with the Approved Document K checks done for you. If the staircase is going into a loft, the Loft Conversion Cost Calculator helps budget the wider job, and the Timber Calculator sizes the stringer and tread timber.

Disclaimer: This guide is for planning to Approved Document K in England and Wales. It is not a structural or building control design. Headroom, guarding, fire escape and site conditions all affect a real staircase, and Scotland and Northern Ireland follow separate standards. Confirm any staircase against the current regulations and your building control officer.