Work out the stair
Total rise is finished floor to finished floor. Enter the going you want; the calculator picks the fewest risers that pass, or set the number yourself.
| Risers | Rise | 2R+G | Pitch | OK? |
|---|
Pitch line length is the slope from the bottom nosing line to the top floor. Stringers need extra for the top and bottom cuts — set out full size before ordering timber.
A guide to the Approved Document K limits (England). Building control has the final say — check the full document and any site-specific requirements.
Stair rules — Approved Document K
Approved Document K (2013 edition, England), Section 1.
| Stair | Rise | Going | Max pitch |
|---|---|---|---|
| Private stair | 150–220 | 220–300 | 42° |
| Utility stair | 150–190 | 250–400 | — |
| General access stair | 150–170 | 250–400 | — |
For all three: 2R + G between 550 and 700 mm. Private = within one dwelling. Utility = escape, access for maintenance or any purpose other than the usual route between levels in buildings other than dwellings. General access = the usual route in other buildings and common areas of flats.
| Total rise | Risers | Rise | Going range | Min total going |
|---|---|---|---|---|
| 2,400 | 11 | 218.2 | 243–263 | 2,430 |
| 2,450 | 12 | 204.2 | 227–291 | 2,497 |
| 2,500 | 12 | 208.3 | 232–283 | 2,552 |
| 2,550 | 12 | 212.5 | 237–275 | 2,607 |
| 2,600 | 12 | 216.7 | 241–266 | 2,651 |
| 2,650 | 13 | 203.8 | 227–292 | 2,724 |
| 2,700 | 13 | 207.7 | 231–284 | 2,772 |
| 2,750 | 13 | 211.5 | 235–276 | 2,820 |
| 2,800 | 13 | 215.4 | 240–269 | 2,880 |
| 2,850 | 13 | 219.2 | 244–261 | 2,928 |
| 2,900 | 14 | 207.1 | 231–285 | 3,003 |
Going range meets the 220 mm minimum, 2R + G of 550–700 mm and the 42° maximum pitch. Total going = (risers − 1) × going.
How to work out risers and going
- Measure the total rise from finished floor to finished floor — allow for floor finishes, screed and boards at both levels.
- Divide by the maximum rise (220 mm for a private stair) and round up to get the fewest risers. Every rise in a flight must be the same.
- Choose a going so that 2R + G is between 550 and 700 mm and, for a private stair, the pitch is no more than 42°.
- Treads = risers − 1 (the top “tread” is the landing). Total going = treads × going.
Example: 2,640 mm total rise ÷ 220 = 12 risers of exactly 220 mm. With a 250 mm going: 2R + G = 690 mm ✓, pitch = tan⁻¹(220 ÷ 250) = 41.3° ✓. Eleven treads give a total going of 2,750 mm.
Why 42° matters
The maximum rise and minimum going (220 + 220) cannot be used together on a private stair: 220/220 is 45°. At a 220 mm rise the going has to be at least 245 mm to stay within 42°.
Headroom
Approved Document K asks for at least 2.0 m clear headroom over the whole stair, measured vertically from the pitch line, and over landings. In a loft conversion where there is not enough space, a reduced headroom is accepted: 1.9 m at the centre line of the stair, reducing to 1.8 m at the side.
Other points to check
- Level treads with consistent rise and going throughout the flight.
- Open risers in dwellings: treads overlap at least 16 mm and a 100 mm sphere must not pass through the gap.
- More than 36 risers in consecutive flights need at least one change of direction.
- Outside dwellings: no more than 16 risers per flight on utility stairs and 12 on general access stairs (exceptionally 16 in small premises).
Questions joiners ask
What is the maximum rise for a stair in a house?
Approved Document K allows a maximum rise of 220 mm and a minimum going of 220 mm for a private stair, with 2R + G between 550 and 700 mm and a maximum pitch of 42°. Because of the pitch limit, a 220 mm rise needs a going of at least about 245 mm.
How many steps for a 2.6 m floor height?
With a private stair, 2,600 mm ÷ 220 = 11.8, so 12 risers of about 217 mm. The going then needs to be roughly 241–266 mm to meet the 42° pitch and the 2R + G rule. There will be 11 treads.
What is the 2R + G rule?
Twice the rise plus the going should be between 550 and 700 mm. It keeps the step comfortable: for example a 200 mm rise with a 250 mm going gives 650 mm.
What headroom does a loft conversion stair need?
Normally 2.0 m above the pitch line. In a loft conversion where that cannot be achieved, Approved Document K accepts 1.9 m at the centre line of the stair reducing to 1.8 m at the side.
More free calculators
Flooring calculator — Laminate, LVT and engineered packs, underlay, skirting, screed› Plasterboard calculator — Boards, screws, tape and jointing for walls and ceilings› Brick calculator — Bricks, mortar, sand and cement for a wall› All free calculators for UK trades›Run your crew and jobs from the phone
Clock-in, timesheets, quotes and CIS pay runs for joiners and small trade firms. First 3 months free.
See GraftumA guide to the Approved Document K limits (England). Building control has the final say — check the full document and any site-specific requirements.