Stair calculator
How many risers a staircase needs, how high each is, how long it runs, and whether it meets BCA's rules in Singapore. Enter the floor-to-floor height; the answer and the section update as you type.
17 risers of 173.5 mm.
- Treads
- 16 × 250 mm
- Length of the run
- 4.00 m
- Landings
- none needed
- 2 × rise + tread
- 597 mm (comfortable)
| Riser175 mm or less · E.3.4.1 | 174 mm | pass |
| Tread225 mm or more · E.3.4.2 | 250 mm | pass |
| Clear width1,000 mm or more · E.3.3.1 | 1,000 mm | pass |
| Risers in a flight18 or fewer, then a landing · E.3.5.2 | 17 | pass |
BCA's rules for staircases
From BCA’s Approved Document, as explained in its Understanding the Approved Document. The clause is the one to look up.
| Riser height | 175 mm at most, all the same (within 5 mm) in a flight | E.3.4.1, E.3.4.4 |
| Tread (going) | 225 mm at least inside a home; 275 mm on a common stair | E.3.4.2 |
| Tapered tread (spiral, winder) | measured 500 mm from the narrow end | E.3.4.3 |
| Clear width | 1000 mm at least, wall to rail or rail to rail | E.3.3.1 |
| Landings | at every floor; between floors after 18 risers at most (not spirals); 1000 mm wide; no step in a landing | E.3.5 |
| Winders | inside a home only: one per quarter turn, with a tread between | E.3.5.4 |
| Handrail | on at least one side of a flight of more than 5 steps, 800–1000 mm above the nosings | E.3.6.1, E.3.6.2 |
| Barrier on an open side | 1000 mm at least, measured from the nosings | H.3.2.1 |
| Gaps | none a 100 mm ball can pass: between balusters, and between open treads | H.3.4.3 |
| Headroom | 2000 mm at least over every step and landing | C.3.2.1 |
A house built by its owner for their own use is exempt from the rules on width, treads and risers, and landings (E.2.4); barriers, gaps and headroom still apply.
Figures often quoted that are not the rule
- “Risers 150 to 180 mm”: the limit is 175 mm. A comfortable stair is nearer 165–175 mm, but 180 does not pass.
- “900 mm wide for a house”: the Approved Document asks for 1,000 mm clear, unless the house is owner-built for their own use.
- “A landing after 16 risers”: it is 18.
- “250 mm treads in a house”: 225 mm is the minimum inside a home; 250 is more comfortable, and it is what the calculator starts from.
- “A 900 mm handrail is enough on an open side”: the handrail may be 800 to 1,000 mm, but the barrier on an open side must be at least 1,000 mm.
An example
A floor to floor of 3,200 mm needs 19 risers of 168.4 mm: more than 18, so two flights of 10 with a landing between, 17 treads of 250 mm and a run of 5.25 m. A more usual 2,950 mm (2.7 m ceiling and a 250 mm slab) takes 17 risers of 173.5 mm in one flight, 4 m long.
Draw it in your plan
Setout’s staircases are built to these rules: straight, L-shaped, U-shaped, winder, spiral, in timber, concrete, open-riser, floating or on a central spine. Place one in the designer, add the floor above, and its panel shows this check and its section; the opening upstairs gets its guard rail on its own.
Questions
What is the maximum riser height in Singapore?
175 mm (BCA Approved Document, E.3.4.1), with every riser in a flight the same height to within 5 mm.
What is the minimum tread for stairs in a house?
225 mm inside a home, 275 mm on a common staircase (E.3.4.2). A spiral or winder tread is measured 500 mm from its narrow end.
How many steps before a landing?
At most 18 risers in a flight; then a landing at least 1000 mm wide (E.3.5.2, E.3.5.3). Spiral staircases are the exception.
How high must a stair railing be?
A handrail sits 800 to 1,000 mm above the nosings; a barrier on an open side must reach at least 1,000 mm, with no gap a 100 mm ball can pass (E.3.6.2, H.3.2.1, H.3.4.3).
Do I need approval to build a staircase?
A new or altered staircase is structural building work: a Qualified Person, an architect or professional engineer, designs it and submits it for approval. The calculator and the check help you plan; they are not a submission.