British thermal unit (BTU)
1 British thermal unit = 1,055.05585262 joules
What is British thermal unit?
A British thermal unit (BTU) is an energy unit defined as the heat needed to raise one pound of water by one degree Fahrenheit. It is used in HVAC systems, heating and cooling equipment ratings, and natural gas billing in the United States.
Notes: Heating/cooling
Real-world uses
The British Thermal Unit is used in the United States for heating and cooling system ratings (furnaces, air conditioners), natural gas billing, and refrigeration. A typical home air conditioner might be rated at 12,000–24,000 BTU/h. Natural gas is often sold per therm (100,000 BTU).
History
The British Thermal Unit was proposed in the 1840s as the heat needed to raise one pound of water by one degree Fahrenheit. Despite its name, its primary use today is in the United States; the UK and most Commonwealth countries have transitioned to SI units for engineering applications.
Common mistakes
Confusing BTU (energy) with BTU/h (power). An air conditioner rated at "12,000 BTU" typically means 12,000 BTU per hour of heat removal capacity, not a fixed energy amount. Also mixing up the slightly different BTU definitions (IT, thermochemical, 39°F, 60°F).
When is this conversion used?
Converting between British thermal unit and joule is common when working across metric and imperial systems, such as international trade, travel between countries with different measurement standards, or following instructions from a different region. Electricity bills use kilowatt-hours while physics calculations use joules. Converting between them is essential for energy audits, comparing appliance efficiency, and understanding power consumption.
How to convert British thermal unit to joule
To convert British thermal unit to joule, multiply the value by 1,055.05585262.
Conversion formula (from base unit)
x * 1055.05585262
Measurement standards
The joule is the SI derived unit of energy, defined as one kilogram-metre-squared per second-squared (kg·m²/s²). The kilowatt-hour, equal to exactly 3.6 megajoules, is accepted for use with the SI by the BIPM for practical electricity metering.
Did you know?
A single bolt of lightning releases roughly 1 to 5 gigajoules of energy, yet only a small fraction reaches the ground as electrical current. Most of the energy dissipates as light, heat, and the thunder shockwave.
| British thermal units | joules |
|---|---|
| 0.1 | 105.50558526 |
| 0.5 | 527.52792631 |
| 1 | 1,055.05585262 |
| 2 | 2,110.11170524 |
| 5 | 5,275.2792631 |
| 10 | 10,550.5585262 |
| 25 | 26,376.3963155 |
| 50 | 52,752.792631 |
| 100 | 105,505.585262 |
| 250 | 263,763.963155 |
| 500 | 527,527.92631 |
| 1,000 | 1,055,055.85262 |
Common values
| British thermal units | joules | |
|---|---|---|
| A food calorie (1 kcal) | 3.96566683 British thermal units | 4,184 joules |
| A AA battery | 8.87156825 British thermal units | 9,360 joules |
| Boiling a kettle | 398.08319053 British thermal units | 420,000 joules |
| Daily human diet (2000 kcal) | 7,931.33366278 British thermal units | 8,368,000 joules |
| 1 gallon of gasoline | 124,884.38377248 British thermal units | 131,760,000 joules |
Full British thermal unit conversion table
| Unit | Value | Factor |
|---|---|---|
| joule | 1 BTU = 1,055.05585262 J | × 1,055.05585262 |
| kilojoule | 1 BTU = 1.05505585 kJ | × 1.05505585 |
| kilowatt hour | 1 BTU = 0.00029307 kWh | × 0.00029307 |
| calorie (thermochemical) | 1 BTU = 252.16440072 cal | × 252.16440072 |
| kilocalorie (dietary) | 1 BTU = 0.2521644 kcal | × 0.2521644 |
| watt hour | 1 BTU = 0.29307107 Wh | × 0.29307107 |
| megajoule | 1 BTU = 0.00105506 MJ | × 0.00105506 |
| electronvolt | 1 BTU = 6.585141e+21 eV | × 6.585141e+21 |
| therm (US) | 1 BTU = 0.00001 therm | × 0.00001 |