How do I fit a staircase into a fixed length?
Published · Updated · By Sai Nath
Divide the total rise by a riser of about 175 to 190 mm to get a whole number of risers. Treads are one fewer. Divide your run by the treads to get the going, then check riser, going and 2R + G against your rules. If the going is too short, you need more run or a different stair.
How do I work out the steps when the run is fixed?
A fixed length gives you two numbers: the total rise (floor to floor) and the total run (the length of floor the stair can use). The only thing you can still choose is the number of risers. Everything else follows from it.
- Measure the total rise from the top of the lower finished floor to the top of the upper finished floor, and the total run from the first riser to the last riser, along the floor.
- Pick a riser count. Rise ÷ a riser of about 190 mm, rounded to a whole number. Riser = rise ÷ risers.
- Count the treads. Treads = risers − 1.
- Find the going. Going = run ÷ treads.
- Check 2R + G (twice the riser plus the going), and the riser and going against your rules.
The other way round tells you what a stair needs: run needed = treads × going. At a 240 mm going, 14 treads need 3360 mm.
Worked example: 2700 mm of rise in 2800 mm of run
- 2700 ÷ 190 = 14.21, which rounds to 14 risers. Riser = 2700 ÷ 14 = 192.9 mm.
- Treads: 14 − 1 = 13.
- Going: 2800 ÷ 13 = 215.4 mm.
- 2R + G = 2 × 192.9 + 215.4 = 601.1 mm.
- Pitch (riser ÷ going): arctan(192.9 ÷ 215.4) = 41.8 degrees.
The 2R + G sum looks fine, which is the trap. The sum can pass while the going and the riser individually fail. Check each one.
Does it pass?
Checked on 28 October 2026. Rules differ by country, and your council or building certifier decides what applies to your job.
- Australia (NCC 2022 Housing Provisions, Table 11.2.2a). A stair that is not spiral has a riser of 115 to 190 mm, a going of 240 to 355 mm and 2R + G of 550 to 700 mm. A flight has 2 to 18 risers. Adjacent risers or goings may differ by no more than 5 mm. Source: NCC 2022 Housing Provisions, Part 11.2.
- England (Approved Document K, 2013 edition for use in England, Table 1.1). A private stair has a rise of 150 to 220 mm, a going of 220 to 300 mm and a maximum pitch of 42 degrees. Twice the rise plus the going is normally 550 to 700 mm. Source: Approved Document K (PDF) via GOV.UK.
New Zealand rules are not covered here. For NZ work, read the current Building Code clause D1 and its Approved Document at the official source.
Against those limits, the example above fails in Australia twice: the 192.9 mm riser is over 190 mm, and the 215.4 mm going is under 240 mm. In England the 14-riser version also fails: the 215.4 mm going is under 220 mm. The sums for each country follow.
What if the going comes out too short?
You have four ways out. Each one trades something.
- Change the riser count. More risers lower the riser but shorten the going, because there are more treads to share the same run. With 15 risers in 2800 mm: riser 180.0 mm, 14 treads, going 200.0 mm, 2R + G 560.0 mm. The riser now passes and the going is worse. More risers never fixes a short run.
- Use fewer, taller risers where the rules allow it. In England the cap is 220 mm. 2700 ÷ 220 = 12.3, so 13 risers: riser 207.7 mm, 12 treads, going 2800 ÷ 12 = 233.3 mm, 2R + G 648.7 mm, pitch 41.7 degrees. That passes the Approved Document K limits above. Australia stops at 190 mm, so this is not available there.
- Find more run. The Australian minimum for this rise is 15 risers at 180 mm and 14 treads at 240 mm: 14 × 240 = 3360 mm. That is 560 mm more than the 2800 mm in the example. Check whether a wall, a cupboard or the stair opening can move that far.
- Change the stair type. A landing with a turn (an L or U shape) uses the length twice, and winders turn within the corner. Alternating-tread and spiral stairs have their own rules, with different limits again; the NCC table above gives separate figures for spiral stairs. This page does not cover how to design any of them.
Can I make the stair steeper to save length?
Only up to the limit. Run falls as the pitch rises, but the riser and going limits stop you first. In England, the 42 degree maximum pitch is a separate cap. A steeper stair is also harder to use, so check the nosing, the handrail and the headroom with your certifier before you commit to the tightest option.
How much length does a stair need for a given rise?
Run needed = (risers − 1) × going. For 2700 mm of rise the sums come out as below. The first row is the Australian minimum going. The second is the English stair with the shortest going that stays within the 42 degree pitch limit.
| Rise 2700 mm | Risers | Riser | Treads | Going | Run | 2R + G |
|---|---|---|---|---|---|---|
| Australia, minimum going | 15 | 180.0 mm | 14 | 240 mm | 3360 mm | 600 mm |
| England, 42 degree pitch | 13 | 207.7 mm | 12 | 231 mm | 2772 mm | 646.4 mm |
| Fixed run 2800 mm | 14 | 192.9 mm | 13 | 215.4 mm | 2800 mm | 601.1 mm |
Where 231 mm comes from: tan 42 degrees is 0.900, so the going must be at least 207.7 ÷ 0.900 = about 230.7 mm, rounded up to 231 mm. Then 12 × 231 = 2772 mm of run.
These sums use the riser rounded to one decimal place. For the rise itself, see how many steps for a floor height; to measure it properly, see how to measure the total rise.
How do I do it in MeisterCalc?
- Open MeisterCalc and tap Stairs on the home screen.
- Choose Rise + Run in the mode toggle below the diagram.
- Enter the Total Rise (2700) and the Total Run (2800). Open the collapsed Advanced section and check Desired Riser Height is 190, which is its default.
- Read Number of Risers (14), Actual Riser Height (192.9 mm), Number of Treads (13) and Actual Tread Width (215.4 mm). A live diagram updates as you type.
- In Advanced, tick the Riser Limited option to always round the riser count up. With 190 mm it gives 15 risers, a 180.0 mm riser and a 200.0 mm tread width.
The same screen shows Stringer Length and the stairwell opening from the floor thickness and headroom you enter; see stairwell opening size. The Incline Angle there is arctan(total rise ÷ total run), which reads a little higher than the riser-over-going pitch above. For the 2700 and 2800 case it shows 43.96° against 41.8 degrees. When you compare against a pitch limit, use the riser and going.
For the 2R + G sum and the wider method, see the 2R + G formula and how to calculate stairs.
What this doesn't do
- It doesn't show 2R + G in Rise + Run mode. Add it up by hand, as above.
- It doesn't design landings, winders, spiral or alternating-tread stairs, or check headroom against your real ceiling, stair width or handrails.
- It doesn't decide what is allowed. The NCC, Approved Document K or the NZ Building Code, and your council or certifier, do. The ranges the screen flags are the app's own, not a rule.
- It is Android only, on Android 7.0 or later, and works offline. There is no iPhone version yet.
Try it
Stairs is one of three MeisterCalc calculators that are free to use, along with Concrete and Check Square. You can join the iOS waitlist.