Stair Calculator
Work out the number of steps, riser height, going and stringer length for your staircase, and instantly check it against UK Building Regulations Part K.
Calculate Your Stair Dimensions
Enter your total rise (floor-to-floor height) and your preferred riser height and going, and we’ll work out how many steps you need, the exact measurements, and whether the design meets UK Building Regs.
Staircase Dimension Calculator
Get your step count, riser, going and stringer length instantly.
How it Works
Understanding the stair calculation
Divide the Rise
We divide your total floor-to-floor height by your preferred riser height and round up, so every step ends up the same height.
Work Out the Going
The number of treads is one fewer than the number of risers, since the top step is the landing itself. Multiplying by your going gives the total horizontal run.
Stringer & Pitch
Using the total rise and total going as two sides of a right-angled triangle, we calculate the stringer length and the pitch angle of the staircase.
Regulation Check
We compare your riser, going and pitch against the UK Building Regs Part K limits for your chosen staircase type.
Standard Stair Dimensions
Maximum riser height and minimum going by staircase type, as set out in Approved Document K.
| Staircase Type | Max Riser | Min Going | Max Pitch |
|---|---|---|---|
| Private Stair | 220mm | 220mm | 42° |
| Utility Stair | 190mm | 250mm | 38° |
| Common / Shared Stair | 170mm | 250mm | 38° |
| Comfortable Domestic Norm | 170–190mm | 250mm | ~35° |
| Minimum Headroom (all types) | 2000mm, measured vertically above the pitch line of the stair | ||
Regulations & Safety Tips
What to keep in mind once you’ve got your numbers.
Building Regulations
UK Building Regs Part K essentials
- Key Rules
- Riser height must not exceed 220mm on a private stair.
- Going must not be less than 220mm on a private stair.
- Pitch must not exceed 42° for a single dwelling.
- Minimum headroom of 2000mm above the pitch line throughout.
- Handrails required on at least one side where the stair rises over 600mm.
Safety & Comfort Tips
Practical advice from experienced builders
- Watch Out For
- Keep every riser on a flight within 5mm of the others to avoid trip hazards.
- Use the 2R + G comfort rule (ideally 550–700mm) alongside the regs, not instead of them.
- Allow extra timber length for the birdsmouth cuts when cutting stringers.
- Check door swing and landing clearance at the top and bottom of the flight.
- Confirm final measurements with building control before you start cutting.
Stair Calculator FAQ
Answers to the most frequently asked questions about calculating and building a staircase in the UK.
Divide your total rise, the vertical floor-to-floor height, by your target riser height, typically around 170 to 190mm for a comfortable domestic staircase. Round the result up to a whole number to get the number of risers, then divide the total rise by that number to get the exact riser height each step will use.
Under UK Building Regulations Part K, a private domestic staircase must have a riser no taller than 220mm and a going no shorter than 220mm. Most builders design closer to a 170 to 190mm riser with a 250mm going, which feels more comfortable to walk than the regulatory maximum.
The 2R + G rule is a comfort formula stating that twice the riser height plus the going should fall between 550mm and 700mm. It is used to check that a staircase has a natural, comfortable stride, since risers and goings that are individually within regulations can still feel awkward together if this total is off.
UK Building Regulations Part K set a maximum pitch of 42 degrees for a private staircase within a single dwelling. Staircases serving more than one dwelling, such as in flats, are usually limited to a shallower pitch for added safety.
Stringer length is the diagonal distance from the bottom of the stairs to the top, found using the total rise and total going as the two shorter sides of a right-angled triangle. In practice, timber is usually cut a little longer than this calculated figure to allow for the birdsmouth notches where the treads sit.