Staircase calculator
Give it a floor-to-floor height and a going, and it gives every number of risers the table permits — and separately, which of them the 2R+G footnote calls normal. They are not the same question. Nothing you type here leaves your browser — it is worked out on your own device, so there is nothing to send and nothing to log.
Approved Document K, 2013 edition, for use in England. Wales, Scotland and Northern Ireland have their own documents with different numbers, and every edition supersedes the last. This is one table read from the PDF on gov.uk — your building control body or approved inspector is the only authority that counts.
2R + G is a footnote, not a rule
Almost every stair calculator treats “twice the rise plus the going, between 550 and 700” as a pass or a fail. The regulation does not. Approved Document K says, in paragraph 1.3:
Use any rise between the minimum and maximum with any going between the minimum and maximum, that complies with the relevant note contained in table 1.1.
And 2R + G appears only as a footnote to the table:
The normal relationship between the dimensions of the rise and going is: twice the rise plus the going (2R + G) equals between 550mm and 700mm.
Normal, not required. The two questions come apart constantly. At a 2,600 mm floor height with a 220 mm going, twelve and thirteen risers sit inside the 550–700 band and are illegal, because the pitch exceeds 42°. Sixteen and seventeen fall outside the band and are perfectly lawful. Across floor heights from 2.0 to 3.2 m and goings from 220 to 300, the two verdicts disagree on about one option in six.
So this page gives them separately: what the regulation permits, and what the footnote calls normal.
Table 1.1, as printed
| Stair | Rise | Going | Pitch |
|---|---|---|---|
| Private | 150–220 mm | 220–300 mm | 42° max |
| Utility | 150–190 mm | 250–400 mm | — |
| General access | 150–170 mm | 250–400 mm | — |
A staircase that is legal in a house is often not legal in an office: the maximum rise drops from 220 mm to 170. And for dwellings, external tapered steps need a going of at least 280 mm.
One more riser than treads. Always.
This is the classic mistake in stair work. A flight climbing to a landing has a riser at the top with no tread on it, because the landing is that tread. So fourteen risers means thirteen treads, and the flight measures thirteen goings — 2,860 mm at a 220 going, not 3,080.
Get it wrong by one and the stair is 220 mm too long for the opening, which is how a staircase ends up not fitting the hole it was measured for.
Two metres of headroom, measured from the pitch line
Not from the tread: from the pitch line, the notional line joining the nosings. Two metres clear, all the way up and over the landings. It is the constraint that most often decides how many risers you can actually have, because the trimmer at the top of the opening is where it runs out.
What this page does not check
Handrails, guarding, landing sizes, tapered treads and winders, open risers, nosing profiles, fire escape, and whether the stair fits the opening. Approved Document K covers all of it; this covers one table of it. The figures here are the 2013 edition, for England — Wales, Scotland and Northern Ireland have their own documents with different numbers, and every edition supersedes the last.
What it will not do
- It will not design a staircase. It tells you which rise-and-going combinations the table permits for the height you have.
- It will not handle winders, tapered treads or a stair that changes direction.
- It will not replace your building control body or an approved inspector, who is the only person whose opinion on this counts.