Cooling capacity gets written three ways — BTU per hour, kilowatts and tons — and converting between them is just two divisions. Divide BTU/hr by 3,412 for kilowatts, or by 12,000 for tons. Here are the formulas, a chart of the common sizes, and the one unit trap to avoid.
The two conversions
| To get | Do this | Because |
|---|---|---|
| kW from BTU/hr | BTU/hr ÷ 3,412 | 1 kW = 3,412 BTU/hr |
| Tons from BTU/hr | BTU/hr ÷ 12,000 | 1 ton = 12,000 BTU/hr |
| kW from tons | tons × 3.517 | 1 ton = 3.517 kW |
Examples: 12,000 BTU to kW is 12,000 ÷ 3,412 = 3.5 kW. 24,000 BTU to tons is 24,000 ÷ 12,000 = 2 tons. To go back, multiply: 5 kW is 5 × 3,412 ≈ 17,060 BTU/hr.
BTU to kW to tons — the common sizes
| BTU/hr | kW | Tons |
|---|---|---|
| 9,000 | 2.6 kW | 0.75 ton |
| 12,000 | 3.5 kW | 1 ton |
| 18,000 | 5.3 kW | 1.5 ton |
| 24,000 | 7.0 kW | 2 ton |
| 30,000 | 8.8 kW | 2.5 ton |
| 36,000 | 10.6 kW | 3 ton |
| 48,000 | 14.1 kW | 4 ton |
| 60,000 | 17.6 kW | 5 ton |
BTU / kW / Ton Converter
Enter any figure in BTU/hr, kW or tons and read off the others — watts and kcal/h too, with common AC sizes listed.
What is a “ton” of cooling?
A ton of refrigeration is 12,000 BTU/hr — about 3.52 kW. The name is historical: it is the cooling you get from melting one US ton of ice over 24 hours, from the era when icewas the refrigeration industry. It survives mainly in American equipment sizing, where a “3-ton” unit means 36,000 BTU/hr.
The unit trap: BTU vs BTU/hr
A BTU is a quantity of energy; cooling and heating capacity is really BTU per hour — a rate. When a spec sheet or search says “12,000 BTU,” it means 12,000 BTU/hr. The conversions above assume that, so a “24,000 BTU” unit is 2 tons of continuous cooling, not a one-off amount.
Capacity is not the electricity it uses
These units all describe the heat the system moves, not the power it draws. A 3.5 kW-cooling unit typically consumes only around 1 kW of electricity, because a heat pump shifts several times more heat than the energy it uses. To estimate the electrical draw, divide the capacity by the unit’s EER or COP — don’t confuse the 3.5 kW of cooling with 3.5 kW off the meter.
What about horsepower (HP)?
In some markets aircons are sold by nominal horsepower, where 1 HP ≈ 9,000 BTU/hr(2.6 kW) — a marketing convention, not the mechanical 746 W horsepower. Treat an HP label as a size class and check the datasheet BTU or kW figure for the real capacity.