Air Conditioner Size Calculator
Work out what size air conditioner you need in under 30 seconds. Enter your room dimensions, ceiling height, insulation and sun exposure, and this aircon size calculator returns the kW capacity that suits the space. It then matches that figure to split systems and box air conditioners we have available, from 1.7kW for small bedrooms up to 9.5kW for open-plan living.
What size air conditioner do I need?
Answer five quick questions and we'll match you to a split system that fits your room. Prices and stock come straight from our store.
Find the perfect air conditioner to fit your room
You need a 2.5kW split system
Reverse-cycle split systems that suit your room, closest match first. Prices exclude installation.
Or a 2.7kW box air conditioner
Window and wall units. There is no outdoor unit, so installation is simpler.
Air conditioner size chart (m² to kW)
A guide for a standard 2.4m ceiling, average insulation and moderate sun. Poor insulation, west-facing glass and raked ceilings all push the figure up. The calculator above accounts for them.
| Room size | Typical room | Capacity |
|---|---|---|
| Up to 12 m² | Study, nursery, small bedroom | 1.7 – 2.0 kW |
| 12 – 20 m² | Bedroom, home office | 2.0 – 2.6 kW |
| 20 – 30 m² | Large bedroom, small living room | 2.6 – 3.5 kW |
| 30 – 45 m² | Living room, rumpus | 3.5 – 5.0 kW |
| 45 – 60 m² | Large living area | 5.0 – 6.0 kW |
| 60 – 80 m² | Open-plan kitchen and living | 6.0 – 7.1 kW |
| 80 – 100 m² | Large open plan | 7.1 – 8.5 kW |
| Over 100 m² | Whole floor or multiple rooms | Multi-head or ducted |
Frequently asked questions
What size air conditioner do I need?
Allow roughly 125 to 160 watts per square metre of floor area, then adjust for ceiling height, insulation, how much sun the room gets and what the room is used for. A 20 m² bedroom lands near 2.5kW and a 50 m² open-plan living area is closer to 7kW. Split systems cover about 1.7kW to 9.5kW for a single head. Window and wall box units stop around 6kW and only suit one enclosed room, so anything larger or open plan needs a split system.
How do I calculate what size air conditioner I need?
Multiply the floor area by the watts per square metre for the room type, then apply three adjustments. Divide the ceiling height by 2.4 for anything above a standard ceiling. Add about 12% for a west or north-facing room and take 10% off a shaded one. Add 15% for poor insulation and take 10% off a well-insulated room. A 16 m² bedroom with a 2.4m ceiling, average insulation and moderate sun works out at 16 × 135 = 2,160 watts, or 2.2kW. The calculator at the top of this page runs the same maths and matches the answer to stock.
How many kW air conditioner do I need for my room size?
As a starting point for a standard 2.4m ceiling: up to 12 m² needs 1.7 to 2.0kW, 12 to 20 m² needs 2.0 to 2.6kW, 20 to 30 m² needs 2.6 to 3.5kW, 30 to 45 m² needs 3.5 to 5.0kW and 45 to 60 m² needs 5.0 to 6.0kW. Above 60 m² you are into 6.0 to 7.1kW and beyond. The size chart further down this page sets out the full range, and box units are only available across the lower half of it.
What size air conditioner do I need for a bedroom?
Most Australian bedrooms fall between 9 and 20 m², which puts them in the 1.7 to 2.6kW range. A small room with good insulation and little direct sun may only need 1.7 to 2.0kW. Bedrooms are usually easier to cool than a living area of the same size because fewer people use them and there is no heat from cooking. Both split systems and box units are available at these capacities, so either will do the job in a closed bedroom.
What size room will a 2.5kW air conditioner cool?
A 2.5kW unit suits roughly 15 to 20 m², which is a standard bedroom or study. For the sizes either side of it: 1.7kW covers up to about 12 m², 3.5kW covers about 20 to 28 m², 5.0kW about 30 to 40 m² and 7.1kW about 45 to 55 m². Insulation, ceiling height and west-facing glass all shift these figures, which is why the calculator asks about them.
What is the biggest window or box air conditioner?
Box units, also called window or wall units, top out around 6kW, which covers a single enclosed room of roughly 30 m². They cannot serve an open-plan area whatever their rated capacity, because the air only reaches one space. Above 30 m², or for anything open plan, a split system is the right answer. Check the physical cut-out dimensions too, since both the capacity and the chassis size vary between models and the opening in your wall or window has to match.
What size ducted air conditioner do I need?
A ducted design covers the whole area rather than one room, and it also depends on zoning, duct runs and available ceiling space. The calculator on this page sizes single rooms for split systems and box units. If your total area is more than one split system can handle, get in touch or visit your local store and we will work through a ducted or multi-head design with you.
This sizer estimates capacity from floor area, ceiling height, insulation, sun exposure and room type. Window glazing, climate zone and door openings change the result too, so treat it as a guide and confirm the final size with your local store.
