Offcut WorksStair calculator
Enter the floor to floor height and the space you have. You get every number of risers that works, with the riser, going and pitch checked against the rules for private stairs in England.
How the numbers are worked out
Riser = total rise ÷ number of risers. A staircase with n risers has n − 1 treads, because the top floor is the last step. Going = run ÷ treads, or the going you chose. Pitch = the angle whose tan is riser ÷ going. 2R+G = twice the riser plus the going.
For 2,600 mm and 13 risers: 2600 ÷ 13 = 200 mm risers and 12 treads. With a 250 mm going the pitch is 38.7° and 2R+G is 650 mm, which passes.
The limits used
| Check | Private stairs |
|---|---|
| Rise | 150 to 220 mm |
| Going | 220 to 300 mm |
| Pitch | 42° maximum |
| 2R+G | 550 to 700 mm |
What this checks and what it does not
The limits come from Approved Document K, Table 1.1, for private stairs in England. They apply to stairs that are part of a building. For free-standing garden steps, use the deck steps calculator.
It does not check headroom, width, handrails, guarding, landings, winders or tapered treads, or other rules in the Approved Document. Wales, Scotland and Northern Ireland have their own regulations. Building control or an architect will confirm the design.
Choosing between options
The suggestion is the passing option whose 2R+G is closest to 600 mm, the middle of the usual range. That is only a guide to comfort. A shallow stair takes more floor space, and a steep one takes less, so pick the option that suits the room.
Measuring
- Measure floor to floor in finished levels, including floor coverings on both floors.
- All the risers in a flight should be the same, and all the goings too. The calculator divides the rise equally.
- Take the available run from the top riser to where the bottom riser will stand, allowing for the nosing.
Questions
How many steps do I need for a staircase?
Divide the floor to floor height by a riser of about 170 to 220 mm. The calculator lists every whole number that works. The number of treads is one less than the number of risers.
What is the maximum riser height for a staircase?
For private stairs in England, Approved Document K allows risers of 150 to 220 mm, and goings of 220 to 300 mm.
What is 2R+G?
Twice the riser plus the going. For private stairs the guide is 550 to 700 mm. It checks that the stairs are not too steep or too shallow to walk comfortably.
Does this apply to garden steps?
Approved Document K applies to steps that are part of a building. Free-standing garden steps are outside it. Use the deck steps calculator.
Where the defaults come from
Show the 1 source
- Approved Document K (2013, England). Table 1.1 for private stairs: rise 150 to 220 mm, going 220 to 300 mm, maximum pitch 42 degrees, and 2R+G normally 550 to 700 mm.
- The suggestion that 600 mm is the best 2R+G is our own way of ranking options, not a rule.
- We checked the table limits only. Other parts of the Approved Document, and the regulations outside England, were not checked here.
- The 250 mm preferred going is a common starting point, not a requirement.