Calculate the cooling/heating capacity needed for your room — in kW and BTU/hr (AU) or tons of cooling (US) — based on climate zone and room size, in metres or feet.
Enter your room dimensions below and pick your units — the calculator recommends an AC size in kW/BTU-hr (AU) or tons of cooling (US), the way air conditioners are actually rated and sold in each market.
| Item | Value |
|---|
| kW | BTU | Room size | Est. cost |
|---|---|---|---|
| 2.0 kW | ~6,800 | Up to 15 m² | $600–900 |
| 2.5 kW | ~8,500 | Up to 20 m² | $700–1,100 |
| 3.5 kW | ~12,000 | 20–30 m² | $900–1,500 |
| 5.0 kW | ~17,000 | 30–45 m² | $1,100–2,000 |
| 7.0 kW | ~24,000 | 45–65 m² | $1,500–2,800 |
| 9.0 kW | ~30,700 | 65–80 m² | $2,000–3,500 |
Reverse-cycle split systems are the most energy-efficient heating and cooling option in Australia. The Energy Rating Label (displayed on all appliances sold in Australia) shows star ratings and kWh consumption to help compare models.
The National Construction Code (NCC) divides Australia into 8 climate zones. Darwin (Zone 1) and Cairns (Zone 2) are hot-humid. Sydney (Zone 5), Melbourne (Zone 6), and Adelaide (Zone 5) are temperate. Hobart and alpine areas (Zones 7–8) are cool to cold.
Look for a high star rating (6+ stars) and a high COP (Coefficient of Performance). A 5.0 kW unit with COP of 4.0 produces 5 kW of cooling while consuming only 1.25 kW of electricity. The Energy Rating website (energyrating.gov.au) lists all rated products.
Air conditioning capacity in Australia is commonly quoted in both BTU/hr and kilowatts (kW). Choosing the right size unit for your room prevents energy waste, poor humidity control, and premature unit failure.
| Room Area (m²) | Temperate (Melbourne/Sydney) | Hot-Humid (Brisbane/Darwin) |
|---|---|---|
| 10-15 m² (bedroom) | 2.0-2.5 kW | 2.5-3.5 kW |
| 15-25 m² (main bedroom) | 2.5-3.5 kW | 3.5-5.0 kW |
| 25-35 m² (living room) | 3.5-5.0 kW | 5.0-7.0 kW |
| 35-60 m² (open plan) | 6.0-8.0 kW | 8.0-12.0 kW |
Air conditioners are rated differently depending on the market. Australian split systems are rated in kilowatts (kW), with BTU/hr sometimes shown alongside. US central and residential AC units are rated in tons of cooling — a legacy unit based on the cooling power of melting one US ton of ice per day. Use the Metric/US toggle above the calculator to switch between room measurements in metres or feet and get a recommendation in the unit that matches how AC is sold in your market.
| Measure | Australia | United States |
|---|---|---|
| Rating unit | Kilowatt (kW) | Ton of cooling |
| 1 unit equals | 3,412 BTU/hr | 12,000 BTU/hr |
| Conversion | 1 kW = 0.284 tons | 1 ton = 3.517 kW |
| Common residential sizes | 2.0-9.0 kW | 1.5-5.0 tons |
What size air conditioner do I need for a bedroom?
For a typical 15 m² (160 sq ft) bedroom: 2.0-2.5 kW (about 0.7-0.85 tons) in cooler climates; 2.5-3.5 kW (0.85-1 ton) in warmer climates. A unit that's too small runs continuously and struggles; too large cycles on and off frequently without properly dehumidifying the air. Use this calculator for an initial estimate and confirm with an HVAC professional.
What is the difference between BTU, kW and tons for air conditioning?
All three measure cooling capacity. 1 kW = 3,412 BTU/hr, and 1 ton = 12,000 BTU/hr = 3.517 kW. Australian units are rated in kW, US residential and central AC units are rated in tons (with BTU/hr often shown too). A 12,000 BTU/hr unit equals both 3.5 kW and 1 ton of cooling.
How many tons of AC do I need for my house?
A common US rule of thumb is about 1 ton per 400-600 sq ft, adjusted for climate, insulation, ceiling height and sun exposure — which is exactly what this calculator's inputs account for. Switch to US units, enter your room or home dimensions in feet, and it recommends a standard ton size (1.5, 2, 2.5, 3, 3.5, 4 or 5 tons).
Is a 2.5 kW or 3.5 kW air conditioner better for a bedroom?
For a standard 15 m² bedroom in a temperate climate, 2.5 kW is usually sufficient and slightly more energy-efficient than an oversized 3.5 kW unit. In hot-humid climates, 3.5 kW is more appropriate due to higher temperatures and humidity. When in doubt, choose the slightly larger unit — an oversized unit is less damaging than an undersized one.
What size AC unit for a 3 ton house?
A "3 ton" AC unit provides 36,000 BTU/hr (about 10.5 kW) of cooling capacity — typically enough for a home of roughly 1,500-1,800 sq ft (140-165 m²) depending on climate and insulation. Oversizing a central system wastes energy and shortens equipment life through short-cycling, so it's worth calculating your actual load rather than guessing by house size alone.