Convert between joules, calories, kilowatt-hours, BTU, electronvolts, and more. Calculate energy conversions for physics, engineering, and daily life.
| Unit | Symbol | Joules Equivalent | Common Uses | Example |
|---|---|---|---|---|
| Joule | J | 1 J | SI unit, all energy forms | Energy to lift 100g 1m high |
| Calorie | cal | 4.184 J | Food energy, chemistry | Energy to heat 1g water 1°C |
| Kilocalorie | kcal | 4,184 J | Nutrition, food labeling | Food Calories (with capital C) |
| Kilowatt-hour | kWh | 3,600,000 J | Electrical energy billing | 1 hour of 1000W appliance |
| British Thermal Unit | BTU | 1,055.06 J | Heating, air conditioning | Energy to heat 1 lb water 1°F |
| Electronvolt | eV | 1.602×10⁻¹⁹ J | Atomic physics, particle physics | Energy gained by electron in 1V |
| Erg | erg | 10⁻⁷ J | Physics (CGS system) | Small energy measurements |
| Foot-pound | ft·lb | 1.35582 J | Mechanical engineering | Torque, mechanical work |
1 food Calorie (with capital C) = 1 kilocalorie = 4,184 joules. Nutritional labels use Calories (kcal).
1 kWh = 3.6 million joules. A 100W bulb running for 10 hours uses 1 kWh of electrical energy.
1 BTU ≈ 1055 joules. It's the energy needed to heat 1 pound of water by 1°F at sea level.
1 electronvolt (eV) = 1.602×10⁻¹⁹ J. Chemical bonds are typically 1-10 eV per bond.
Sun delivers ~1,360 W/m² to Earth. In 1 hour, 1 m² receives about 4.9 million joules.
1 liter gasoline contains ~34.2 MJ. A car engine is about 20-30% efficient in converting this to motion.
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