Stair calculator
How many steps a flight needs, how deep each one is, and whether it meets the guidance for a house in England.
Every number of steps that could fit
| Risers | Rise | Going | Pitch | 2R + G | Guidance |
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Checked against Approved Document K, 2013, Table 1.1, for a private stair in England. Figures read 11 Sep 2026.
Rise, going, and the two rules that tie them
The rise of a step is the height from one tread's top surface to the next. The going is its depth, measured nosing to nosing. For a stair in a house, Approved Document K puts the rise between 150 mm and 220 mm and the going between 220 mm and 300 mm, and every step in a flight has to have the same rise and the same going.
Two further rules decide most flights. The pitch, the angle of a line joining the nosings, can be no steeper than 42°. And twice the rise plus the going has to come to between 550 mm and 700 mm, which keeps a step in proportion to a stride. A stair can pass the first two limits on their own and still fail this one.
The top step is not a tread
A flight of 13 risers has 12 treads, because the last step up lands on the floor above. Counting a tread for every riser is the classic mistake, and it makes the flight one going too long or every step too shallow. The page divides the space by the treads, not the risers.
Headroom
There has to be at least 2 m of clear height above the pitch line of the flight and above every landing. A loft conversion that cannot manage that may have 1.9 m at the centre of the stair, falling to 1.8 m at the side. The page cannot check headroom, because it depends on the ceiling over the stair, so measure it before settling on a design.
What this does not check
It covers a straight flight in a single house. It does not cover winders or other tapered treads, which are measured differently, or landings, handrails, guarding and open risers, all of which Approved Document K also covers. It is guidance for England: Wales, Scotland and Northern Ireland each have their own. And an Approved Document is guidance rather than law, so a flight that meets it is one that building control should accept, and a flight that does not may still be agreed, most often in an existing house. The roof pitch calculator and the triangle calculator do the same trigonometry for other jobs.
Common questions
- What is the maximum rise for a stair in a house?
- 220 mm a step, and at least 150 mm. The going, the depth of each step, has to be between 220 mm and 300 mm, the pitch can be no steeper than 42°, and twice the rise plus the going has to come to between 550 mm and 700 mm. Those are the figures for a private stair in Table 1.1 of Approved Document K, which is the guidance for houses in England.
- Why does twice the rise plus the going matter?
- It keeps each step in proportion to a normal stride. A step can pass the rise limit and the going limit separately and still be awkward to climb, too shallow and deep or too tall and short, and this is the rule that catches it. It is where most flights that look fine on paper fail.
- Does this apply in Wales or Scotland?
- No. Wales has its own Approved Document K, an older edition with different figures: it has no minimum rise and no maximum going, and allows some other combinations. Scotland follows the Building Standards Technical Handbook, and Northern Ireland Technical Booklet H. This page checks the figures for England only.
- What if an old house cannot meet these figures?
- Approved Document K expects existing buildings to follow the same table unless their dimensions make it impossible. Where they do, the alternative has to be agreed with the building control body. Talk to them before building, not after.
- How much headroom does a staircase need?
- At least 2 metres, measured above the pitch line of the flight and above each landing. A loft conversion that cannot reach that may have 1.9 m at the centre of the stair, falling to 1.8 m at the side. This page does not check headroom, because it depends on the ceiling above the flight.