Buying Guide · Singapore · Updated September 2026
What Size Aircon Do You Need?
Enter your room size below. Most Singapore bedrooms need 9,000 or 12,000 BTU, and most living rooms 18,000 or 24,000 BTU.
Aircon BTU calculator
Measure the room wall to wall, in metres.
12.0 m² room · works out to about 7,200 BTU
9,000 BTU · 2.6 kW · 1 hp
Rounded up to the next size actually sold. Treat this as a starting point: we confirm the size when we quote your installation.
Aircon size by room size
For a normal room with average sun. Go one size up for west-facing or top-floor rooms.
Up to 15 m²
Study, small or common bedroom (most HDB common bedrooms are around 10–13 m²)
9,000 BTU
15–20 m²
Master bedroom
12,000 BTU
20–30 m²
Living room in a 3- or 4-room flat
18,000 BTU
30–40 m²
Larger or open-plan living and dining area
24,000 BTU
Over 40 m²
Or a ceiling cassette or ducted unit, sized on site
Two units
How the size is worked out
BTU measures how much heat an aircon can remove from a room in an hour. The bigger the room and the more heat coming in, the more BTU you need.
For Singapore's climate, the usual rule is about 600 BTU for every square metre of floor. A 4 m × 3 m bedroom is 12 m², which works out to about 7,200 BTU, so it gets the smallest common size, 9,000 BTU.
Then adjust for what heats the room up:
West-facing: add 10%
The afternoon sun hits the wall and windows during the hottest part of the day, and the room keeps that heat into the evening, just when you want it cool.
Top floor: add 10%
The roof takes the full sun all day with no flat above to shade it, so heat comes down through the ceiling as well as the walls.
More than two people: add 600 BTU each
Every person gives off heat. It matters most in a living room where the family gathers, or a bedroom shared by more than two.
Finally, round up to the next size you can actually buy for a wall-mounted unit: 9,000, 12,000, 18,000 or 24,000 BTU. A west-facing room on the top floor can need a full size bigger than the floor area alone suggests.
Why getting the size right matters
Too small
- • Runs all the time and still never gets the room properly cold.
- • Higher electricity bills, because it never gets to ease off.
- • The compressor works flat out every day, so it wears out sooner.
Too big
- • Cools too fast and switches off before it removes the moisture, so the room feels cold and clammy.
- • Switches on and off more often, which wastes power and wears the parts.
- • Costs more to buy for no benefit.
BTU, kW and horsepower
Aircon boxes and quotes use all three. To turn BTU into kW, divide by 3,412. The “hp” figure is a rough label that shops use, not a real measurement.
9,000
BTU
2.6 kW
1 hp
12,000
BTU
3.5 kW
1.5 hp
18,000
BTU
5.3 kW
2 hp
24,000
BTU
7.0 kW
2.5 hp
Sizing a System 2, 3 or 4
With a multi-split system, each indoor unit is sized for its own room using the rule above. A System 3 for a flat might be 9,000 + 9,000 + 12,000 BTU for two common bedrooms and the master bedroom.
The outdoor unit is then matched to that combination. Brands publish which indoor and outdoor units can be paired, so this part is picked from their list rather than calculated. Not sure what System 1 to 4 means? See the types of aircon explained.
Common questions
What BTU aircon do I need for a bedroom in Singapore?
Most common bedrooms (around 10–13 m²) need a 9,000 BTU unit. A master bedroom of 15–20 m² usually needs 12,000 BTU. Go one size up if the room is west-facing or on the top floor.
What BTU aircon do I need for a living room?
A living room of 20–30 m² usually needs 18,000 BTU, and a larger open-plan living and dining area of 30–40 m² needs 24,000 BTU. Beyond about 40 m², two units, or a ceiling cassette or ducted unit, usually works better than one big wall unit.
How do I calculate aircon BTU?
Multiply the floor area in square metres by about 600. Add 10% for a west-facing room, 10% for a top-floor room, and 600 BTU for each extra person beyond two. Then round up to the next size sold: 9,000, 12,000, 18,000 or 24,000 BTU.
Is it bad to buy an aircon that is too big?
Yes. An oversized aircon cools the room too quickly and switches off before it has pulled the moisture out of the air, so the room feels cold but clammy. It also switches on and off more often, which wastes electricity and wears the compressor faster.
How do I convert BTU to kW?
Divide the BTU figure by 3,412. A 9,000 BTU aircon is about 2.6 kW, 12,000 BTU is about 3.5 kW, 18,000 BTU is about 5.3 kW, and 24,000 BTU is about 7 kW.
Does an inverter aircon change the size I need?
Not the size you should buy. An inverter slows down once the room is cool, so it copes better with a room that is slightly on the big side, but the room still needs enough capacity to cool down on a hot afternoon.
Buying a new aircon?
Send us your room sizes on WhatsApp and we will confirm the right size for each room when we quote the installation, so you do not end up with the wrong unit. See aircon installation.