Energy Unit Converter
The energy unit converter allows you to convert between commonly used energy measurements such as joules, calories, BTU, kilowatt-hours, and electronvolts. This tool is useful for physicists, engineers, nutritionists, and anyone working with energy calculations. Select a conversion below or choose from popular energy unit conversions.
Supported Energy Units
| Unit | Short Form | Description |
|---|---|---|
| Joule | J | SI derived unit of energy, N⋅m |
| Kilojoule | kJ | 1,000 joules, common in nutrition |
| Megajoule | MJ | 1,000,000 joules |
| Millijoule | mJ | 1/1,000 of a joule |
| Erg | erg | CGS unit of energy, 10^-7 joules |
| Watt-hour | Wh | Energy equivalent to 1 watt for 1 hour |
| Kilowatt-hour | kWh | 1,000 watt-hours, used for electricity billing |
| British Thermal Unit | BTU | Energy to raise 1 lb of water by 1°F |
| Electronvolt | eV | Energy gained by electron in 1V potential |
| Kiloelectronvolt | keV | 1,000 electronvolts |
| Megaelectronvolt | MeV | 1,000,000 electronvolts, nuclear physics |
| Gigaelectronvolt | GeV | 1,000,000,000 electronvolts, particle physics |
| Calorie | cal | Energy to raise 1g of water by 1°C |
| Kilocalorie | kcal | 1,000 calories, dietary “Calorie” |
Popular Energy Conversions
- Joule to Calorie
- Calorie to Joule
- Kilowatt-hour to Joule
- BTU to Joule
- Kilocalorie to Kilojoule
- Electronvolt to Joule
How Energy Unit Conversion Works
Energy units are converted using fixed mathematical ratios based on fundamental physical definitions.
For example, 1 joule equals 0.239 calories, 1 kilowatt-hour equals 3,600,000 joules, and 1 BTU equals approximately 1,055 joules.
Our energy converter uses accurate conversion factors to ensure precise results for physics, nutrition, and engineering applications.
Common Use Cases
- Nutrition and dietary energy calculations
- Electricity consumption and billing
- HVAC system specifications
- Physics and chemistry calculations
- Renewable energy system design
Frequently Asked Questions
How accurate is the energy unit converter?
Our converter uses precise conversion factors based on international standards. Results are accurate to multiple decimal places, suitable for professional use in science, engineering, and nutrition.
What is a joule?
A joule (J) is the SI derived unit of energy. It’s the energy transferred when a force of one newton moves an object one meter. One joule is also one watt-second.
How many joules are in a calorie?
1 calorie equals approximately 4.184 joules. This is the “small calorie” or gram calorie. The dietary “Calorie” (capital C) is actually a kilocalorie (1,000 calories = 4,184 joules).
What’s the difference between calories and Calories?
A calorie (lowercase) is 4.184 joules. A Calorie (capital C), also called a kilocalorie or dietary calorie, is 1,000 calories or 4,184 joules. Food labels use Calories (kilocalories).
How many joules are in a kilowatt-hour?
1 kilowatt-hour (kWh) equals exactly 3,600,000 joules (3.6 megajoules). This is the unit typically used on electricity bills.
What is a BTU?
A British Thermal Unit (BTU) is the energy required to raise the temperature of one pound of water by one degree Fahrenheit. It equals approximately 1,055 joules and is commonly used in HVAC systems.
What is an electronvolt?
An electronvolt (eV) is the energy gained by an electron when accelerated through a potential difference of one volt. It equals approximately 1.602×10^-19 joules and is commonly used in atomic and particle physics.
How do I convert kilocalories to kilojoules?
To convert kilocalories (kcal) to kilojoules (kJ), multiply by 4.184. For example, 100 kcal equals 418.4 kJ. Many food labels show both values.