What is the BTU/hr to Watts Calculator?
This calculator converts thermal or cooling power measured in British Thermal Units per hour (BTU/hr) into electrical power measured in watts (W). It is widely used when sizing air conditioners, heaters, refrigeration, and HVAC equipment, where capacity is often rated in BTU/hr but energy consumption and motor ratings are expressed in watts or kilowatts.
How to use it
Enter the power value in BTU per hour and the calculator instantly displays the equivalent in watts and kilowatts. For example, a typical 12,000 BTU/hr "1-ton" air conditioner converts to roughly 3,517 watts of thermal capacity.
The formula explained
The conversion is based on the fact that 1 watt equals approximately 3.412 BTU/hr. To go the other way, you divide:
$$\text{Power (W)} = \frac{\text{Power (BTU/hr)}}{3.412}$$
To express the result in kilowatts, divide the watts by 1,000. The factor 3.412 (more precisely 3.41214) comes from the definition of the BTU and the watt-hour relationship.
Worked example
Suppose an appliance is rated at 10,000 BTU/hr. Dividing by 3.412 gives \(10{,}000 \div 3.412 \approx 2{,}930.83\) watts, or about 2.93 kW.
Conversion Constants
Converting between BTU per hour (BTU/hr) and watts (W) relies on the fixed thermodynamic relationship between the British Thermal Unit and the joule. The watt is an SI unit defined as one joule per second, while the BTU/hr is a rate of energy delivery. The constants below use the International Table BTU (IT BTU), which is the value most commonly cited in HVAC, refrigeration and appliance ratings.
| Relationship | Value |
|---|---|
| 1 watt | 3.41214 BTU/hr (IT) |
| 1 BTU/hr | 0.29307107 W |
| 1 kilowatt | 1,000 W |
| 1 kW | 3,412.14 BTU/hr |
The exact IT conversion factor is \(1\ \text{W} = 3.41214\ \text{BTU/hr}\), so the precise reverse conversion is:
$$\text{Power (W)} = \frac{\text{Power (BTU/hr)}}{3.41214}$$This calculator uses the rounded divisor 3.412 for quick everyday conversions. The difference between 3.412 and the precise 3.41214 is about 0.004%, which is negligible for sizing heaters, air conditioners and other equipment but may matter in precision engineering work.
Be aware that there is more than one definition of the BTU. The thermochemical BTU differs slightly from the International Table BTU, giving \(1\ \text{W} \approx 3.41443\ \text{BTU/hr}\) (about 0.07% larger). Unless a data sheet specifies otherwise, equipment ratings use the IT BTU, so the 3.41214 value is the appropriate constant for nearly all practical conversions.
FAQ
Is 3.412 the same as 3.41214? The widely used rounded conversion factor is 3.412 BTU/hr per watt. For higher precision, 3.41214 can be used; the difference is negligible for most equipment sizing.
Does this measure electricity use? Not directly. BTU/hr ratings on air conditioners describe cooling/heating capacity, not power drawn from the wall. The watt figure here is the equivalent power in SI units, useful for comparison.
How do I convert watts back to BTU/hr? Multiply watts by 3.412 to return to BTU per hour.
