Stair Calculator guide
Stair Calculator: Risers, Treads and UK Building Regulations
Use our stair calculator to work out the number of steps, riser height, going and pitch for a staircase, checked against Approved Document K.
By the AllCalculator editorial teamUpdated 16 October 20261 min read
A comfortable, safe staircase needs every step the same, with the right balance of height and depth. Our Stair Calculator works out the dimensions and checks them against the Building Regulations for England.
How to use the calculator (Stair Calculator)
- Choose the type of stair: private (in a home), utility or general access.
- Enter the total rise: the height from finished floor to finished floor.
- Enter the going: the depth of each tread, measured from the front of one step to the front of the next.
You'll see the number of risers and treads, the riser height, the total run, the pitch and the regulation checks.
The rules (Approved Document K)
| Stair type | Rise | Going |
|---|---|---|
| Private | 150–220mm | 220–300mm |
| Utility | 150–190mm | 250–400mm |
| General access | 150–170mm | 280–425mm |
Also:
- 2 × rise + going should be between 550mm and 700mm.
- The pitch of a private stair must be no more than 42°.
- There must be at least 2m of headroom (with some exceptions for loft conversions).
A worked example
With the calculator's default settings, a total rise of 2,600mm with a 240mm going needs 13 risers of 200mm and 12 treads. The pitch is 39.8° and 2R + G is 640mm, so every check passes.
Frequently asked questions
Why is there one less tread than risers?
The top step is the floor you arrive on.
Do Scotland, Wales and Northern Ireland have the same rules?
No. Each has its own building regulations, with slightly different limits.
Do I need building control approval?
Usually, for a new or replacement staircase. Check with your local authority or an approved inspector before you start.
Sources and further reading
- GOV.UK: Approved Document K – protection from falling, collision and impactgov.uk
- GOV.UK: Approved Documentsgov.uk
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This guide is general information to help you understand your options. It isn't financial, tax, legal or building advice and doesn't take your personal circumstances into account. Figures were checked when the guide was last updated and can change, so confirm anything important with GOV.UK, HMRC, a regulated adviser or a qualified tradesperson.