Energy Converter
Convert between joules, calories, kWh, BTU, and more.
How to Use Energy Converter
- 1Enter an energy value
- 2Select the source unit
- 3See all other unit equivalents instantly
About Energy Converter
The Energy Converter converts between all common energy units: joules, kilojoules, calories, kilocalories (food Calories), watt-hours, kilowatt-hours, megawatt-hours, BTU, foot-pounds, and electron-volts. Enter any energy value and see all other equivalents immediately.
The converter spans every major energy domain: joules and kilojoules for scientific physics calculations, calories and kilocalories for nutrition and chemistry, kilowatt-hours for electricity billing, BTU for heating and cooling systems, and electron-volts for particle physics.
All processing runs locally in your browser with no server communication. Whether you are calculating home electricity consumption, comparing food energy content, or solving physics problems, results are accurate and instant.
Key Features of Energy Converter
- Convert between joules (J), kilojoules (kJ), and megajoules (MJ)
- Convert between calories (cal) and kilocalories/food Calories (kcal)
- Convert between watt-hours (Wh), kilowatt-hours (kWh), and MWh
- Includes BTU for heating, cooling, and US energy contexts
- Includes foot-pounds for mechanical energy
- Includes electron-volts (eV) for particle physics
- All equivalents shown simultaneously in one view
- Instant results as you type
Supported Formats
Input Formats
Output Formats
1 kcal = 4,184 J. 1 kWh = 3,600,000 J. 1 BTU = 1,055.06 J. 1 calorie (cal) = 4.184 J.
Examples
Convert food Calories to kilojoules
Convert a 500 kcal meal to kilojoules for a nutrition label.
Input
500 kcal
Output
2,092 kJ | 2,092,000 J | 0.5817 kWh
Convert BTU to kWh for HVAC
Convert the energy output of a 12,000 BTU air conditioner to kWh.
Input
12,000 BTU
Output
3.517 kWh | 12,663 kJ | 3,024 kcal
Common Use Cases
- Converting food Calories to kilojoules for international nutrition labels
- Calculating household electricity consumption in kWh from joules
- Comparing HVAC system capacities in BTU and kWh
- Physics homework converting between different energy units
- Chemistry calculations converting caloric energy to joules
- Understanding energy storage capacity for batteries and fuel
Troubleshooting
Confusing calorie (cal) with Calorie (kcal)
Solution
1 food Calorie (capital C) = 1 kilocalorie (kcal) = 1,000 small calories (cal). Nutrition labels always use kcal, sometimes written as "Calories." The small calorie is mainly a chemistry unit.
Expecting joules and watt-seconds to be different
Solution
1 joule = 1 watt-second exactly. They are the same unit expressed differently. 1 watt-hour = 3,600 joules.
Confusing BTU per hour (power) with BTU (energy)
Solution
BTU is a unit of energy. BTU/hour is a unit of power (rate of energy flow). This converter handles energy (BTU), not power (BTU/h). For power, use the power converter.
Frequently Asked Questions
What is the difference between cal and kcal?
1 kcal (kilocalorie or food Calorie) = 1,000 cal (small calories). Food nutrition labels use kcal, often written as "Calories" with a capital C. In chemistry, the small calorie (4.184 J) is used.
How many joules are in a kilowatt-hour?
1 kWh = 3,600,000 joules (3.6 MJ). This is because 1 kW = 1,000 W = 1,000 J/s, and 1 hour = 3,600 seconds.
What is a BTU?
A BTU (British Thermal Unit) is the energy needed to raise 1 pound of water by 1°F. 1 BTU = 1,055.06 joules. It is commonly used in the US for heating, cooling, and natural gas energy.
What is an electron-volt?
An electron-volt (eV) is the energy gained by an electron moving through 1 volt of electric potential. 1 eV = 1.602 x 10^-19 joules. It is used in particle physics and atomic-scale energy measurements.
How many kcal are in 1 kWh?
1 kWh = 3,600,000 J / 4,184 J/kcal = 860.4 kcal. This is useful when comparing dietary energy to electricity consumption.
Is this useful for comparing food energy to electricity costs?
Yes. You can convert the caloric content of your daily food intake to kWh and compare it to the energy usage of household appliances, providing an interesting perspective on human energy consumption.
Can I convert MWh for large-scale energy calculations?
Yes. The converter handles megawatt-hours accurately, which is useful for utility-scale energy projects, industrial consumption reporting, and battery storage systems.
Is my data private?
Yes. All conversions run entirely in your browser. No values are transmitted to any server.