BTU to Joules Conversion: Calculator, Chart and Formula Explained
1 BTU = 1,055.06 joules (J). Formula: Joules = BTU × 1,055.06. Reverse: BTU = Joules ÷ 1,055.06. Quick conversions: 1,000 BTU = 1,055,060 J = 1,055.06 kJ ≈ 1.055 MJ. Use our BTU to joules converter for instant calculations with all related energy units.
BTU to Joules Conversion Table
| BTU | Joules (J) | Kilojoules (kJ) | Megajoules (MJ) |
|---|---|---|---|
| 1 BTU | 1,055.06 J | 1.055 kJ | 0.001055 MJ |
| 5 BTU | 5,275.3 J | 5.275 kJ | 0.005275 MJ |
| 10 BTU | 10,550.6 J | 10.551 kJ | 0.01055 MJ |
| 50 BTU | 52,753 J | 52.753 kJ | 0.05275 MJ |
| 100 BTU | 105,506 J | 105.506 kJ | 0.1055 MJ |
| 500 BTU | 527,530 J | 527.53 kJ | 0.5275 MJ |
| 1,000 BTU | 1,055,060 J | 1,055.06 kJ | 1.055 MJ |
| 5,000 BTU | 5,275,300 J | 5,275.3 kJ | 5.275 MJ |
| 10,000 BTU | 10,550,600 J | 10,550.6 kJ | 10.551 MJ |
| 50,000 BTU | 52,753,000 J | 52,753 kJ | 52.753 MJ |
| 100,000 BTU | 105,506,000 J | 105,506 kJ | 105.506 MJ |
| 1,000,000 BTU | 1.055 × 10⁹ J | 1,055,060 kJ | 1,055.06 MJ |
What Is a BTU?
The British Thermal Unit (BTU) is the amount of heat required to raise the temperature of exactly 1 pound of water by 1 degree Fahrenheit at approximately 39.1°F (the point of maximum water density). Despite the name "British," BTUs are used almost exclusively in the United States — the UK and most of the world use joules, kilojoules, or kilowatt-hours.
You encounter BTUs primarily in:
- Air conditioners: A "12,000 BTU air conditioner" outputs 12,000 BTU/hr of cooling capacity (also called "1 ton of cooling")
- Furnaces and boilers: Heating capacity rated in BTU/hr (e.g., 80,000 BTU/hr = 23.4 kW)
- Natural gas billing: 1 therm = 100,000 BTU ≈ 29.3 kWh
- Food energy (US): 1 food Calorie (kcal) = 3.966 BTU
BTU Conversion Formula Step by Step
BTU to Joules
Joules = BTU × 1,055.06
Example: Convert 2,500 BTU to joules
2,500 × 1,055.06 = 2,637,650 J = 2,637.65 kJ = 2.638 MJ
Joules to BTU
BTU = Joules ÷ 1,055.06
Example: Convert 500,000 J to BTU
500,000 ÷ 1,055.06 = 473.8 BTU
BTU to Other Energy Units: Complete Reference
| From 1 BTU | Equals | Common Use |
|---|---|---|
| Joules (J) | 1,055.06 J | SI unit, physics, engineering |
| Kilojoules (kJ) | 1.05506 kJ | Food energy, chemistry |
| Kilowatt-hours (kWh) | 0.000293071 kWh | Electricity billing |
| Calories (cal) | 252.164 cal | Small calorie, thermochemistry |
| Kilocalories (kcal) | 0.252164 kcal | Food Calories (US nutrition) |
| Watt-hours (Wh) | 0.293071 Wh | Battery capacity, small devices |
| Foot-pounds (ft·lbf) | 778.169 ft·lbf | US mechanical engineering |
| Therms | 0.00001 therms | Natural gas billing (US) |
Practical Examples: BTU to Joules in Real Applications
HVAC: Air Conditioner Energy Output
A 12,000 BTU/hr window air conditioner running for 8 hours:
- Total BTU = 12,000 × 8 = 96,000 BTU
- Joules = 96,000 × 1,055.06 = 101,285,760 J = 101.3 MJ
- kWh equivalent = 101,285,760 ÷ 3,600,000 = 28.13 kWh
- At $0.12/kWh: $3.38 for 8 hours of cooling
Natural Gas: Heating Value
1 cubic foot of natural gas contains approximately 1,020 BTU of energy (varies by source). In joules: 1,020 × 1,055.06 = 1,076,161 J ≈ 1.076 MJ/cubic foot. A furnace consuming 100 cubic feet/hour at 80% efficiency delivers: 100 × 1,020 × 0.80 = 81,600 BTU/hr = 86,093,000 J/hr = 23.9 kW of heating.
Food Energy: BTU and Calories
A 500-calorie meal contains 500 kcal = 2,093 kJ. In BTU: 2,093,000 ÷ 1,055.06 = 1,984 BTU. Your body's metabolic rate of ~2,000 kcal/day = ~7,934 BTU/day = ~9.7 MJ/day — comparable to a 100-watt light bulb running for 112 hours.
BTU vs Joule: Historical Context
The BTU predates the SI unit system. Defined in the 19th century by British engineers, it was based on readily observable experimental conditions: water temperature change is easy to measure. The joule, defined by James Prescott Joule in 1843, became the SI standard because it connects directly to mechanical work (1 J = 1 N·m = 1 kg·m²/s²). Today, engineers in SI countries use kJ and kWh; the US alone maintains BTU as a primary unit in HVAC and energy contexts.
Related Conversion Calculators
- BTU to joules converter — instant calculation tool
- BTU to kWh converter — for electricity cost calculations
- Joules to calories converter
- Watts to BTU/hr converter
Frequently Asked Questions
How many joules are in 1 BTU?
1 BTU = 1,055.06 joules (J). For quick mental math: 1 BTU ≈ 1 kJ. 1,000 BTU ≈ 1.055 MJ. The exact value is 1 BTU = 1,055.05585262 J (International Table BTU definition).
What is the formula to convert BTU to joules?
Joules = BTU × 1,055.06. To convert joules to BTU: BTU = Joules ÷ 1,055.06. For kilowatt-hours: kWh = BTU ÷ 3,412.14 (since 1 kWh = 3,412.14 BTU).
What is the difference between BTU and BTU/hr?
BTU is a unit of energy (quantity). BTU/hr is a unit of power (rate of energy per time). Air conditioners and furnaces are rated in BTU/hr — it describes how much thermal energy they can deliver per hour. If an appliance is rated at 10,000 BTU/hr and runs for 2 hours, it transfers 20,000 BTU total = 21,101,200 J ≈ 21.1 MJ.