Tons ↔ BTU/h ↔ kW Converter
Convert cooling capacity between tons, BTU/h and kW, and see the airflow it implies. One ton of cooling is 12,000 BTU/h — a unit that dates back to the ice trade.
Calculator
3.0 tons = 36,000 BTU/h = 10.55 kW of cooling capacity (1 ton = 12,000 BTU/h; 1 kW = 3,412 BTU/h).
“Tons” is the standard way to talk about air-conditioning capacity in the US, and it confuses everyone the first time. It has nothing to do with weight: one ton of cooling is the rate of heat removal needed to melt one ton of ice in 24 hours, which works out to exactly 12,000 BTU/h. This converter moves between tons, BTU per hour and kilowatts (thermal), and shows the airflow the capacity implies at the standard 400 CFM/ton.
Being fluent in these units lets you compare a mini-split rated in BTU against a central system rated in tons, or a European unit rated in kW against an American one in tons, without second-guessing the arithmetic.
Formula
Two constants do all the work:
BTU/h = tons × 12,000\nkW = BTU/h / 3,412 (1 kW = 3,412 BTU/h)\nCFM = tons × 400 (airflow at 400 CFM/ton)
Basis: 1 ton = 12,000 BTU/h; 1 kWh = 3,412 BTU; ~400 CFM/ton. See Sources.
Worked example
A common 3-ton residential system:
BTU/h = 3 × 12,000 = 36,000 BTU/h\nkW = 36,000 / 3,412 = 10.55 kW\nCFM = 3 × 400 = 1,200 CFM
So 3 tons = 36,000 BTU/h = 10.55 kW, moving about 1,200 CFM of air. The kW figure here is thermal capacity (heat moved), not the electrical power the compressor draws — that depends on efficiency and is handled by the running-cost calculator.
Capacity vs power draw
Thermal kW vs electrical kW. The kilowatts here describe how much heat the system moves, not how much electricity it consumes. A 3-ton (10.55 kW-thermal) AC at EER 12 draws only about 3 kW of electricity. Keep the two straight when you compare a nameplate to a power bill.
Where the “ton” came from. Before mechanical refrigeration, buildings were cooled with delivered ice. Rating a machine by how much ice it replaced per day stuck, and 12,000 BTU/h — one ton of ice melted over 24 hours — became the definition we still use.
Reference table
| Tons | BTU/h | kW (thermal) | Airflow (CFM) |
|---|---|---|---|
| 1.5 | 18,000 | 5.28 | 600 |
| 2.0 | 24,000 | 7.03 | 800 |
| 2.5 | 30,000 | 8.79 | 1,000 |
| 3.0 | 36,000 | 10.55 | 1,200 |
| 3.5 | 42,000 | 12.31 | 1,400 |
| 4.0 | 48,000 | 14.07 | 1,600 |
| 5.0 | 60,000 | 17.58 | 2,000 |
1 ton = 12,000 BTU/h = 3.52 kW thermal; airflow at the standard 400 CFM/ton.
Frequently asked questions
How many BTU is 1 ton of cooling?
Exactly 12,000 BTU/h. It is the heat-removal rate that melts one ton of ice in 24 hours — the historical origin of the unit.
How many kW is 3 tons of cooling?
3 tons = 36,000 BTU/h = 10.55 kW of thermal capacity. That is heat moved, not electricity used.
Is a ton of AC the same as a ton of weight?
No. A ton of cooling is a rate of heat removal (12,000 BTU/h), unrelated to the unit’s physical weight.
How much airflow does a ton of cooling need?
About 400 CFM per ton (350–450 in practice). See airflow from tonnage.