Metric Unit Calculator
The formula, your substituted values, and the evaluated result are shown below.
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View offerAffiliate link — we may earn a commission at no extra cost to you.Estimate air-conditioner capacity.
This is a planning estimate. Confirm dimensions, allowances, material specifications, applicable codes, and supplier requirements before purchasing or construction.
Estimate air-conditioner capacity.
This calculator gives a first-pass cooling capacity for a room by multiplying its floor area by a cooling load per square foot:
Cooling capacity (BTU/h) = room area (ft²) × cooling load (BTU/h per ft²)
A widely used starting point is about 20 BTU/h per square foot for an ordinary room with standard ceilings. The inputs are in square feet because BTU sizing comes from the US. If you measure in metres, multiply m² by 10.764 to get ft².
Split systems don't come in every size. The smallest are typically around 2–2.5 kW, so a room like this would normally get the smallest unit available.
ENERGY STAR's room air-conditioner guidance suggests these adjustments to the basic figure:
Also allow more for high or raked ceilings, poor insulation, large west-facing windows, or an open plan that joins other spaces. In hot Australian climates, installers often size living areas more generously than the US rule of thumb.
Too small, and the unit runs flat out and still can't reach the set temperature on hot days. Too big, and it cools the air quickly then cycles off before removing humidity, leaving the room cold and clammy, and it costs more to buy. For large, open-plan or unusual rooms, get a proper heat-load calculation from a licensed installer rather than relying on a floor-area rule.
| BTU/h | kW | Typical use (rule of thumb) |
|---|---|---|
| 7,000 | 2.1 | Small bedroom or study |
| 9,000 | 2.6 | Bedroom |
| 12,000 | 3.5 | Large bedroom or small living room |
| 18,000 | 5.3 | Living room |
| 24,000 | 7.0 | Large open-plan living area |
At 20 BTU/h per ft², it works out to about 215 BTU/h per m², or roughly 63 W of cooling per m² before adjustments.
One refrigeration ton is 12,000 BTU/h, or about 3.5 kW.
No. The rating is cooling output. Electrical input is usually several times smaller. Check the energy rating label for running costs.