Energy Converter
Convert between joules, calories, kilocalories, BTU, kilowatt-hours and electronvolts.
How to Use the Energy Converter
Convert between joules, kilojoules, calories, kilocalories, BTUs, kilowatt-hours and electronvolts.
- Select the "From" unit — choose the energy unit you want to convert from.
- Enter a value — type any number into the input field. Results update in real time.
- Select the "To" unit — choose the target energy unit.
- Swap if needed — click the swap button to reverse the conversion direction.
- Copy the result — click Copy to send the value to your clipboard.
All conversions run in your browser using standard physical constants.
Frequently Asked Questions
What is the difference between a calorie and a kilocalorie?
1 kilocalorie (kcal) = 1,000 calories (cal). In nutrition, what is commonly called a "Calorie" (capital C) is actually a kilocalorie. So when a food label says 200 Calories, it means 200 kcal or 200,000 calories.
How many joules are in a kilowatt-hour?
1 kWh = 3,600,000 joules (3.6 MJ). A kilowatt-hour is the energy consumed by a 1,000-watt appliance running for one hour.
What is a BTU?
A British Thermal Unit (BTU) is the amount of heat needed to raise 1 pound of water by 1 degree Fahrenheit. 1 BTU = 1,055.06 joules. BTUs are commonly used for heating and cooling ratings in the US.
What is an electronvolt?
An electronvolt (eV) is a very small unit of energy used in particle physics and quantum mechanics. 1 eV = 1.602 × 10⁻¹⁹ joules. It is the energy gained by a single electron when accelerated through 1 volt of electrical potential.
How do I convert food calories to joules?
Multiply food Calories (kcal) by 4,184 to get joules, or by 4.184 to get kilojoules. For example, a 200 Calorie snack = 200 × 4,184 = 836,800 joules = 836.8 kJ.
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