Energy is the capacity to do work. It can exist in various forms such as kinetic, potential, thermal, electrical, chemical, and nuclear energy.

How do I convert joules to kilojoules?

Divide the number of joules by 1,000 to get kilojoules.

How do I convert kilowatt-hours to joules?

Multiply kilowatt-hours by 3,600,000 to get joules.

What is the difference between calorie and kilocalorie?

One kilocalorie (kcal) is equal to 1,000 calories (cal). Nutritional calories are usually kilocalories.

What are the most commonly used energy units?

The most commonly used units are joule (J), kilojoule (kJ), kilowatt-hour (kWh), calorie (cal), electron-volt (eV), and Btu.

Energy Converter

Convert any energy unit quickly and accurately. Whether you need to convert joules to kilojoules, kilowatt-hours to calories, or electron-volts to watt-hours, our tool gives you instant results, clear explanations, and helpful tables – all in one place.

Value

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How to Use the Energy Converter

Enter the value you want to convert.
Select the original unit (From) and the target unit (To).
See the result instantly, along with a human-readable explanation.

This tool supports all major energy units: joule, kilojoule, kilowatt-hour, calorie, electron-volt, Btu, and more.

Popular Energy Conversions

From	To	Formula
Joules (J)	Kilojoules (kJ)	J ÷ 1,000
Kilowatt-hours (kWh)	Joules (J)	kWh × 3,600,000
Calories (cal)	Joules (J)	cal × 4.184
Electron-volts (eV)	Joules (J)	eV × 1.60218×10⁻¹⁹
Btu (IT)	Joules (J)	Btu × 1,055.06
Watt-hours (Wh)	Joules (J)	Wh × 3,600

Energy Units Explained

What is a Joule?

The joule (J) is the SI unit of energy, defined as the energy transferred when applying a force of one newton over a distance of one meter.

What is a Kilowatt-hour?

A kilowatt-hour (kWh) is a unit of energy equal to 3.6 million joules. Commonly used for measuring electrical energy.

What is a Calorie?

A calorie (cal) is a unit of energy. The nutritional calorie (kcal) is equal to 1,000 small calories (cal).

What is an Electron-volt?

An electron-volt (eV) is the amount of kinetic energy gained by a single electron when accelerated through an electric potential difference of one volt.

What is a Btu?

Btu (British thermal unit) is a unit of energy used in the United States, equal to about 1,055.06 joules.

FAQ – Energy Conversion

What is energy?: Energy is the capacity to do work. It can exist in various forms such as kinetic, potential, thermal, electrical, chemical, and nuclear energy.
How do I convert joules to kilojoules?: Divide the number of joules by 1,000 to get kilojoules.
How do I convert kilowatt-hours to joules?: Multiply kilowatt-hours by 3,600,000 to get joules.
What is the difference between calorie and kilocalorie?: One kilocalorie (kcal) is equal to 1,000 calories (cal). Nutritional calories are usually kilocalories.
What is an electron-volt?: An electron-volt (eV) is a very small unit of energy used in atomic and particle physics, equal to 1.60218×10⁻¹⁹ joules.
What are the most commonly used energy units?: The most commonly used units are joule (J), kilojoule (kJ), kilowatt-hour (kWh), calorie (cal), electron-volt (eV), and Btu.