UK stair calculator

Guidance commonly associated with Approved Document K for private stairs (the stair serving a single dwelling) is often summarised as: rise between 150 and 220 mm, going between 220 and 300 mm, a maximum pitch of 42 degrees, and 2R+G falling between roughly 550 and 700 mm.

Headroom of 2 m is also commonly cited for stairs within a dwelling. These figures change between document editions and can vary for stairs outside a dwelling, so treat them as a planning reference rather than a guarantee, and check the current document and your local Building Control before finalising a design.

A typical UK floor-to-floor height between a ground and first floor is commonly in the 2600 to 2700 mm range, depending on the joist depth and floor build-up used. Older properties, particularly Victorian and Edwardian houses, often run higher.

A common resulting layout for that floor-to-floor range is 13 risers, which keeps the individual rise within the commonly cited 150–220 mm band without pushing the going below a comfortable figure.

Take a 2650 mm floor-to-floor height split across 13 risers: rise per riser = 2650 ÷ 13 ≈ 203.8 mm, which sits inside the commonly cited 150–220 mm range.

With a 250 mm going, the pitch works out to atan(203.8 ÷ 250) ≈ 39.2°, under the commonly cited 42° maximum, and 2R+G = 2(203.8) + 250 ≈ 657.7 mm, at the upper edge of the commonly cited 550–700 mm comfort range.

British joinery language calls the sloped board that carries the treads and risers a string, whereas American sources almost always say stringer. They're the same component; if you're reading a mix of UK and US material, don't assume they're describing different parts of the stair.

Similarly, going is the British term for what American sources call tread depth: the horizontal distance from one nosing to the next. Tread, in British usage, more often refers to the horizontal board itself rather than the dimension, which is a subtle but common source of confusion when cross-referencing sources.

Handrail height on UK domestic stairs is commonly cited around 900 mm above the pitch line of the stair, and newel post heights are frequently detailed to a similar figure at the base and top of the flight, though exact numbers depend on the specific staircase design and manufacturer's fixing details.

These figures sit alongside, not instead of, the rise, going and pitch limits above, and like them, should be checked against the current Approved Document K and your Building Control's expectations before a final design is committed to.

Other countries publish their own stair guidance with different numbers; Australian standards, for example, are structured differently from Approved Document K and shouldn't be assumed to match UK figures directly. If you're building outside England and Wales, look up the guidance that actually applies in your jurisdiction rather than reusing these numbers.