What Is a BTU? (BTU Converter)
Understand what a BTU is and convert between BTU per hour, kilowatts, watts and tons of cooling — enter any value to see the equivalents instantly.
What is a BTU?
A BTU — British Thermal Unit — is the amount of heat needed to raise the temperature of one pound of water by one degree Fahrenheit. On its own it’s a tiny amount of energy, so heating and cooling equipment is rated in BTUs per hour: how much heat a system can add or remove in an hour. A higher BTU rating means more capacity.
1 ton = 12,000 BTU/hr · 1 kW = 3,412 BTU/hr · 1 W = 3.412 BTU/hr
BTU conversions
| Value | BTU/hr | kW | Tons |
|---|---|---|---|
| Small window AC | 5,000 | 1.47 | 0.42 |
| One-ton mini-split | 12,000 | 3.52 | 1.0 |
| Two-ton system | 24,000 | 7.03 | 2.0 |
| Three-ton system | 36,000 | 10.55 | 3.0 |
A bigger BTU rating is only better when it matches the space — an oversized unit short-cycles and removes less humidity. To size cooling to a room, use the BTU calculator or the mini split sizing calculator.
Frequently asked questions
What is a BTU?
A BTU, or British Thermal Unit, is the amount of heat needed to raise the temperature of one pound of water by one degree Fahrenheit. In heating and cooling it is used as BTUs per hour — a measure of how much heat a system can add or remove in an hour.
What does BTU mean on an air conditioner?
On an AC or heater, the BTU rating is its capacity per hour — how much heat it can move. A higher BTU rating means more cooling or heating power. The right number depends on the space, so a bigger BTU rating is only better if it matches the room.
How many BTUs are in a kilowatt?
One kilowatt equals about 3,412 BTUs per hour. So to convert kilowatts to BTU/hr, multiply by 3,412; to go from BTU/hr to kilowatts, divide by 3,412. The converter above does this along with watts and tons.
How many BTUs are in a ton of cooling?
One ton of cooling equals 12,000 BTUs per hour — a unit that dates back to the cooling power of a ton of melting ice. A 36,000 BTU system is therefore 3 tons.