Staircase Calculator (UK)
Work out a compliant staircase before you cut a single stringer. This UK staircase calculator takes your floor-to-floor height and returns the number of steps, the individual rise, the going and the pitch, checked against Approved Document K for England and Wales. Pick your stair type, set the going, and it tells you whether the design passes the rise, going, pitch and 2R+G comfort rules — plus the stringer length to order your timber to. It is free, works on your phone on site, and there is a full worked example below.
Most home staircases are Private / domestic.
Finished floor below to finished floor above — not the ceiling height.
Nosing to nosing, not the physical board width. Default 250 mm for this stair type.
If entered, the tool checks whether the stair fits the available floor space.
Enter your floor-to-floor height to size the staircase.
How to use this staircase calculator
- Measure the floor-to-floor height in millimetres — finished floor below to finished floor above.
- Choose the stair type. Most home staircases are Private / domestic.
- Set the going (tread depth). 250 mm is a comfortable, common default.
- Read off the number of steps, rise and pitch, and check the compliance line before you build.
Most joiners land on a rise around 185–200 mm because it feels natural underfoot; the calculator aims for that and then checks it against the regs.
Understanding the numbers
Rise is the vertical height of each step. Going is the horizontal depth of each tread, front to back (not the same as the tread board width, which usually overhangs with a nosing). Pitch is the angle of the whole flight. Get the rise and going right and the pitch and comfort look after themselves.
Approved Document K limits (England & Wales)
| Stair type | Rise min (mm) | Rise max (mm) | Going min (mm) | Max pitch |
|---|---|---|---|---|
| Private / domestic | 150 | 220 | 220 | 42° |
| Utility | 150 | 190 | 250 | — |
| General access | 150 | 170 | 250 | — |
For every stair type, twice the rise plus the going (2R + G) must land between 550 mm and 700 mm — the comfort rule that stops a staircase feeling either cramped or like a ladder.
The 2R + G rule, in plain terms
A step feels right when the rise and going trade off against each other in a fixed way: the steeper each step, the shorter the tread should be. The regs pin that to 2R + G between 550 and 700 mm. A 190 mm rise with a 250 mm going gives 2(190) + 250 = 630 mm — comfortably mid-range. Drift outside the band and the stair either wastes floor space or gets uncomfortably steep.
Worked example: a 2,600 mm floor-to-floor in a Nottingham semi
Say you are fitting a new straight flight in a Nottingham semi with a 2,600 mm floor-to-floor height, a Private stair, and a 250 mm going.
- Steps (risers): 2,600 ÷ 190 ≈ 13.7, rounded to 14 risers
- Individual rise: 2,600 ÷ 14 = 185.7 mm (within the 150–220 mm limit)
- Treads (goings): 14 − 1 = 13
- Pitch: atan(185.7 ÷ 250) = 36.6° (under the 42° limit)
- Horizontal run: 250 × 13 = 3,250 mm (3.25 m)
- 2R + G: 2(185.7) + 250 = 621 mm (inside 550–700)
- Stringer length per side: √(2,600² + 3,250²) = 4,162 mm ≈ 4.16 m
Every check passes, so this is a compliant, comfortable domestic flight. You would order stringer timber at 4.2 m minimum and allow for the newel connections.
A point most stair calculators skip
Plenty of online stair tools will happily return a "valid" staircase that you physically cannot fit, because they ignore the run and the headroom. The going run above is 3.25 m of floor eaten up in a straight line — before landings. If your opening is shorter, you do not just squeeze the going; you switch to a half-landing or a winder, or you lose headroom, which has its own 2,000 mm minimum (1,900 mm at the centre of a loft-conversion stair, 1,800 mm at the edge). Always sanity-check the horizontal run and the headroom against the actual space before you trust the step count.
Headroom and landings (quick reference)
Minimum headroom over the pitch line is 2,000 mm for a normal stair, relaxed to 1,900 mm at the centre and 1,800 mm at the edge for a loft conversion where a full 2 m is not achievable. A straight flight should generally be broken with a landing rather than run on indefinitely; landings must be at least as deep as the stair is wide and kept clear of door swings.
Frequently Asked Questions
Related tools
- Deck Stair Stringer Calculator — external deck steps and stringer layout
- Timber Calculator — work out the stringer, tread and riser timber
- Loft Conversion Cost Calculator — where a new staircase most often gets added
- Floor Joist Span Calculator (UK) — size the joists for the landing and floor above
Guides worth reading
- How to Work Out a Staircase: Rise, Going and Pitch (UK) — step-by-step method, the 2R+G rule and the headroom trap most people miss
Disclaimer: This calculator gives a compliant geometry for planning to Approved Document K (England and Wales). It is not a structural design. Headroom, landings, handrails, guarding, fire escape and the specific site conditions all affect a real staircase. Scotland and Northern Ireland follow separate standards. For a build, confirm the design against the current Approved Document K (or your regional standard) and your building control officer.