How to work out stairs
Back to calculator ↑Riser and tread limits
SCB summarises Ministerial Regulation No. 55 (2000), clause 23, for residential buildings as follows.
- Riser no more than 20 cm
- Net tread at least 22 cm after deducting any overlap
- Flights no more than 3 m high, with a landing above that
- At least 1.90 m of clear headroom above the steps
Confirm the current rules with your district office or municipality before building.
How the steps are worked out
Divide the floor-to-floor height by the target riser and round up. A 3 m height with an 18 cm riser needs 17 risers, each about 17.6 cm. There is one fewer tread than risers, so 25 cm treads take 4 m of floor.
Will it feel comfortable?
A common rule of thumb is that 2 × riser + tread should be about 60–65 cm. This is a comfort guide, not a legal limit.
Common questions
What is the maximum stair riser in a Thai home?
For residential buildings, the riser must be no more than 20 cm and the net tread at least 22 cm.
How many steps does a 3 m stair need?
With a riser of about 18 cm, it needs 17 steps.