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.
United States — national average · 2026 prices
Material only unless stated as installed. Excludes tax, permits and local labour. Verify with local suppliers — see how we calculate.
How this calculator works
Every figure above comes from the formula below, applied to the assumptions listed. Nothing is looked up from a hidden table — you can reproduce the result by hand.
Formula
1 kW = 3,412.142 BTU/hr · 1 W = 3.412142 BTU/hr · 1 ton of cooling = 12,000 BTU/hr
kilowatts = BTU/hr ÷ 3,412.142 · tons = BTU/hr ÷ 12,000
Assumptions & limits
- These are exact unit definitions, not estimates — the only rounding is in the display.
- BTU here means BTU per hour, a rate of heat flow, which is how heating and cooling equipment is rated. A plain BTU is a quantity of energy.
- A ton of cooling is 12,000 BTU/hr by definition, from the cooling effect of melting a ton of ice in 24 hours.
- This converts capacity ratings. It does not convert electrical input to cooling output — that relationship is the unit’s efficiency (SEER or COP), a different figure entirely.
Worked example
Converting a 12,000 BTU/hr air conditioner rating
- Kilowatts = 12,000 ÷ 3,412.142 = 3.517 kW
- Watts = 12,000 ÷ 3.412142 = 3,517 W
- Tons = 12,000 ÷ 12,000 = 1.00 ton
Result:12,000 BTU/hr = 3.517 kW = exactly 1 ton of cooling.
Built and maintained by Christoph Ballmer, Honeygoat GmbH
Method and constants last checked against the calculator code on August 17, 2026. Independent trade review is not yet in place for this calculator — see how we handle review.
Read the site-wide calculation methodology · estimate vs. quote and safety limits
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.
The conversions at a glance
| From | To | Multiply by |
|---|---|---|
| kW | BTU/hr | 3,412 |
| BTU/hr | kW | 0.000293 |
| Tons of cooling | BTU/hr | 12,000 |
| BTU/hr | Watts | 0.293 |
The two confusions worth clearing up
BTU vs BTU per hour. A BTU is an amount of energy; BTU/hr is a rate — power. Equipment ratings are always the rate, colloquially shortened to “BTU”. When a spec sheet says a 12,000 BTU air conditioner, it means 12,000 BTU per hour of heat removal.
Cooling output vs electrical input. A 12,000 BTU/hr unit removes about 3.5 kW of heat but does not consume 3.5 kW of electricity — a heat pump moves heat rather than generating cold, so it might draw only 1 kW. The ratio between the two is the efficiency (EER, SEER or COP), and it is why heat-pump heating beats resistance heating on the power bill.
Sizing actual equipment from a room? That is the BTU calculator for window and portable units and the mini-split calculator for ductless heads.
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.