About this calculator
Quick sizing for a reverse-cycle split system in kW for one room, adjusted for climate, sun, insulation and ceiling height.
How it’s calculated
kW = floor area × a climate rate (about 0.13–0.17 kW per m²) × ceiling height ÷ 2.4 m, adjusted for sun and insulation. The result is rounded up to the next common split system size: 2.0, 2.5, 3.5, 5.0, 6.0, 7.1, 8.0 or 9.0 kW.
Worked example
With these inputs:
- Room length
- 4.5 m
- Room width
- 3.8 m
- Ceiling height
- 2.4 m
- Climate
- Warm (e.g. Sydney, Adelaide, Perth)
- Sun on the room
- Average
- Insulation
- Average
the result is:
- Cooling capacity
- 2.6 kW
- Room area
- 17.1 m²
- Base rate
- 150 W per m²
- In BTU/h
- 8,752
Tips from the trade
- Oversized AC short-cycles and leaves rooms clammy, so bigger is not better.
- Open-plan areas count as one room. Measure the whole space the unit has to cool, not just the part it faces.
Common questions
What size air conditioner for a 30 m² room?
About 4.5 kW in a warm climate with average insulation, so a 5.0 kW split system.
Results are estimates for planning and pricing. Check quantities against your drawings, the manufacturer’s data and the NCC and Australian Standards before ordering.