The corner of the box that is not available
Approved Document K gives a private stair a rise between 150mm and 220mm, and a going between 220mm and 300mm. Read those as two independent ranges and a stair at 220 rise with 220 going looks fine. It even passes the proportion rule: twice the rise plus the going comes to 660mm, comfortably inside the 550 to 700 band.
It is a pitch of 45 degrees. The maximum for a private stair is 42. Table 1.1 does say so, but it says it in a note underneath, and the table's own instruction is to use any rise with any going that complies with the relevant note. The note is not a footnote, it is the rule. Drop it and you get a stair that fails on site having been told twice that it passed.
In practice this means the deeper end of the rise range costs you going. At a 220mm rise the real minimum going is 244mm, not the 220 printed in the table. This tool applies the note first, so the going range it offers you is the one you can actually use.
Work from the floor to floor, because that is what is fixed
Every riser in a flight has to be the same height. That means you do not choose a rise, you choose how many risers to divide the floor-to-floor height into, and the rise falls out of the division. A 2600mm floor to floor gives you anything from 12 risers at 216.7mm to 17 at 152.9mm, and all of them are legal on rise alone.
Measure floor to floor as finished floor to finished floor, not to the joist and not to the ceiling. If the upstairs finish is not decided yet, that is worth settling first: 18mm of engineered board across the landing changes every riser in the flight.
The number that decides it
Whether a stair works is almost never about the rise. It is about the floor space, and that is the run on plan: the number of treads multiplied by the going. A flight has one fewer tread than it has risers, because the top riser lands on the floor above and that is not a tread. Getting that wrong overstates the run by one going, which on a tight loft is the difference between it fitting and not.
Thirteen risers at a 230mm going is twelve treads, so 2.76m of floor, before any landing at either end. That is the figure to take to a drawing, and it is the one this tool leads with.
What this is and what it is not
This tells you what to ask for and roughly what it will take up, so you can price it, draw it, or have a sensible conversation with whoever is designing it. It checks dimensions against the guidance in Approved Document K. It does not design a stair, it does not size a stringer, and it is not a building control submission.
The figures are the 2013 edition for use in England. Scotland, Wales and Northern Ireland have their own documents with their own numbers, and so do the US, Australia and Canada. The dimensions here do not carry across, and a stair set out to the wrong country's code looks completely normal right up until somebody measures it.
Common questions
What is the maximum rise for domestic stairs in the UK?
For a private stair, one serving a single dwelling, the rise must be between 150mm and 220mm and the going between 220mm and 300mm, from table 1.1 of Approved Document K. But the maximum rise and the minimum going cannot be used together, because a private stair also has a maximum pitch of 42 degrees and 220 over 220 is 45.
Why does the calculator say 220 going is too shallow when the table allows it?
Because the table has a note attached and the note is part of the rule. Table 1.1 says to use any rise with any going "that complies with the relevant note", and note 1 caps a private stair at 42 degrees. At a 220mm rise you need at least 244mm of going to stay under that. Most free calculators read the two ranges as independent and pass a stair that would not.
What is the 2R+G rule?
Twice the rise plus the going should come to between 550mm and 700mm. It is a proportion check: a stair can have a legal rise and a legal going and still walk badly if they are mismatched. It does not catch everything, which is the point of also checking pitch.
How much floor space does a staircase need?
The run on plan is the number of treads times the going, and a flight has one fewer tread than it has risers. A typical 2.6m floor to floor at 13 risers and a 230mm going is 12 treads, so 2.76m of floor, before any landing at the top or bottom. That figure is usually what decides whether a loft conversion works.
What headroom do I need over a staircase?
Two metres on the access between levels. For a loft conversion in a dwelling, where 2m genuinely cannot be achieved, Approved Document K diagram 1.4 allows 1.9m at the centre of the stair width reducing to 1.8m at the side. That relaxation is for loft conversions only and it relaxes headroom only, not rise, going or pitch.
How many risers can a flight have?
A utility stair is capped at 16 risers in a flight and a general access stair at 12, exceptionally 16 in small premises where the plan area is restricted. Approved Document K states no flight limit for private stairs. Separately, more than 36 risers in consecutive flights needs at least one change of direction.
Does this apply outside England?
No. The figures here are from Approved Document K, 2013 edition, for use in England. Scotland, Wales and Northern Ireland have their own documents, and the US, Australia and Canada use different codes with different numbers. Do not carry these dimensions across.