Energy Converter – Convert Joules, kWh, BTU, Calories & More
Accurate, instant energy unit conversions between Joules, Kilowatt-hours, British Thermal Units, Calories, Electronvolts, and 14+ units. Perfect for physics, engineering, nutrition, and everyday energy calculations — no sign-up required.
SI base unit: Joule (J). All values are expressed in Joules. Use this table for quick comparison across metric, imperial, and scientific energy units.
| Unit Name | Symbol | Equivalent in Joules (J) | System |
|---|
Instant Energy Unit Conversion – Science & Everyday Use
Energy measures the capacity to do work or produce heat. Our energy converter supports all major units: Joules (J), Kilojoules (kJ), Megajoules (MJ), Gigajoules (GJ), Calories (cal), Kilocalories (kcal), Watt-hours (Wh), Kilowatt-hours (kWh), Electronvolts (eV), Megaelectronvolts (MeV), British Thermal Units (BTU), Therms, Foot-pounds, and Horsepower-hours. Whether you’re calculating electricity bills, food energy, or physics problems, get results instantly.
Understanding Different Energy Units
The Joule (J) is the SI derived unit of energy. One joule equals the energy transferred when applying one newton of force over one meter. In daily life, we often use kilowatt-hours (kWh) for electricity and kilocalories (kcal) for food.
Metric / SI Energy Units
Kilojoule (kJ) = 1,000 J, commonly used in nutrition labels outside the US. Megajoule (MJ) = 1 million J, used for gas and large-scale energy. Gigajoule (GJ) appears in industrial contexts.
Electrical Energy Units
Watt-hour (Wh) and kilowatt-hour (kWh) measure electrical energy consumption. 1 kWh = 3.6 million J. Average household uses several hundred kWh per month.
Thermal & Imperial Units
British Thermal Unit (BTU): widely used for heating and cooling. 1 BTU ≈ 1055 J. Therm = 100,000 BTU, used for natural gas billing. Foot-pound (ft·lb) is a traditional engineering unit for torque/work.
Scientific & Particle Physics
Electronvolt (eV) is tiny: 1 eV = 1.60218 × 10⁻¹⁹ J, used in quantum physics and chemistry. Megaelectronvolt (MeV) = 10⁶ eV, common in nuclear and particle physics.
How to Convert Energy Units: Simple Formula
All conversions are based on the base unit Joule. Multiply the value in the source unit by the conversion factor relative to Joule, then divide by the target unit’s Joule factor. Example: to convert 500 Calories (cal) to Joules: 500 cal × 4.184 J/cal = 2,092 J.
- BTU to J: multiply by 1055.06
- kWh to J: multiply by 3.6e6
- eV to J: multiply by 1.60218e-19
Examples of Energy in Real Life
- Lighting a 10W LED bulb for 1 second consumes 10 Joules.
- One kilocalorie (food calorie) raises temperature of 1 kg water by 1°C.
- A typical smartphone battery stores about 10–15 Wh (36,000–54,000 J).
- One gallon of gasoline contains ≈ 120,000 BTU (≈ 126 MJ).
Quick Energy Conversion Equivalents
| Conversion | Value |
|---|---|
| 1 kWh | 3,600,000 J | 3,412 BTU | 860 kcal |
| 1 BTU | 1,055.06 J | 0.000293 kWh | 252 cal |
| 1 Calorie (kcal) | 4,184 J | 1.162 Wh | 0.00397 BTU |
| 1 eV | 1.602 × 10⁻¹⁹ J |
| 1 Therm | 1.055 × 10⁸ J | 29.3 kWh |