Energy Converter: Convert Joules, Calories, kWh, BTU, and More

Energy is an important part of science, engineering, electricity, food, machines, and everyday life.

An Energy Converter helps you change an energy value from one unit to another. You can convert joules to kilojoules, kilowatt-hours to joules, calories to joules, electronvolts to joules, and more.

Our free online Energy Converter makes energy conversion simple. Enter a value, choose the starting unit, select the unit you need, and get your result in seconds.

You do not need to do difficult math by hand.

What Is Energy?

Energy is the ability to do work or cause a change.

Energy is used everywhere. Electricity, heat, food, batteries, machines, and moving objects all involve energy.

The standard SI unit of energy is the joule.

The symbol for joule is J.

For example:

• A battery stores chemical energy.
• Electricity provides energy to electronic devices.
• Food provides energy to the human body.
• Heat is a form of energy.
• Machines use energy to do work.

Different fields use different energy units. This is why an energy converter can be useful.

What Is an Energy Converter?

An Energy Converter is an online tool that changes an energy value from one unit to another.

For example, you can convert:

• Joules to kilojoules.
• Kilojoules to joules.
• Calories to joules.
• Kilocalories to kilojoules.
• Watt-hours to joules.
• Kilowatt-hours to joules.
• Electronvolts to joules.
• BTU to joules.
• Foot-pounds force to joules.
• Ergs to joules.

Our online Energy Converter supports 11 energy units.

Energy Units and Symbols

The following table shows the units supported by our Energy Converter.

The joule (J) is the standard SI unit of energy.

The size of the unit depends on the prefix or measurement system.

For example:

• 1 kJ = 1,000 J
• 1 MJ = 1,000,000 J
• 1 Wh = 3,600 J
• 1 kWh = 3,600,000 J

How to Use the Energy Converter

Our free online Energy Converter is easy to use.

Follow these steps:

1. Enter the energy value.
2. Select the starting unit.
3. Select the target unit.
4. Read the converted result.
5. Enter another value when you need a new conversion.

For example, enter 5 kJ, select J as the target unit.

The result is:

5 kJ = 5,000 J

The converter can be used for small and large energy values.

Energy Conversion Formula

Energy conversion depends on the relationship between the units.

A simple way to convert an energy value is to first express it in joules and then convert it to the target unit.

For example:

Energy in target units = Energy in joules ÷ joules per target unit

To convert joules to kilojoules, divide by 1,000.

To convert kilojoules to joules, multiply by 1,000.

Common Energy Conversion Formulas

Electronvolt conversions are normally used for very small amounts of energy.

1 eV = 1.602176634 × 10⁻¹⁹ J

Energy Conversion Examples

Example 1: Convert 5 Kilojoules to Joules

One kilojoule is equal to 1,000 joules.

Multiply 5 by 1,000.

5 × 1,000 = 5,000

Answer: 5 kJ = 5,000 J

Example 2: Convert 10,000 Joules to Kilojoules

One kilojoule is equal to 1,000 joules.

Divide 10,000 by 1,000.

10,000 ÷ 1,000 = 10

Answer: 10,000 J = 10 kJ

Example 3: Convert 2 Megajoules to Joules

One megajoule is equal to 1,000,000 joules.

Multiply 2 by 1,000,000.

2 × 1,000,000 = 2,000,000

Answer: 2 MJ = 2,000,000 J

Example 4: Convert 100 Calories to Joules

One thermochemical calorie is equal to 4.184 joules.

100 × 4.184 = 418.4

Answer: 100 cal = 418.4 J

Example 5: Convert 5 Kilocalories to Joules

One kilocalorie is equal to 4,184 joules.

5 × 4,184 = 20,920

Answer: 5 kcal = 20,920 J

Example 6: Convert 2 Watt-hours to Joules

One watt-hour is equal to 3,600 joules.

2 × 3,600 = 7,200

Answer: 2 Wh = 7,200 J

Example 7: Convert 3 Kilowatt-hours to Joules

One kilowatt-hour is equal to 3,600,000 joules.

3 × 3,600,000 = 10,800,000

Answer: 3 kWh = 10,800,000 J

Example 8: Convert 1 BTU to Joules

One International Table BTU is equal to 1,055.056 joules.

Answer: 1 BTU (IT) = 1,055.056 J

Example 9: Convert 10 Foot-pounds Force to Joules

One foot-pound force is approximately equal to 1.355817948 joules.

10 × 1.355817948 = 13.55817948

Answer: 10 ft·lbf ≈ 13.5582 J

Example 10: Convert 1,000,000 Ergs to Joules

One erg is equal to 0.0000001 joules.

1,000,000 × 0.0000001 = 0.1

Answer: 1,000,000 erg = 0.1 J

What Is a Joule?

A joule is the standard SI unit used to measure energy.

The symbol is J.

A joule can be used to measure many types of energy, including mechanical, electrical, thermal, and other forms of energy.

For example:

1 kJ = 1,000 J

1 MJ = 1,000,000 J

Because the joule is part of the SI system, many scientific and engineering calculations use joules as the main energy unit.

What Is a Kilowatt-hour?

A kilowatt-hour, written as kWh, is a unit of energy commonly used for electricity.

Electricity meters often show energy use in kilowatt-hours.

One kilowatt-hour is equal to:

1 kWh = 3,600,000 J

For example, if an electrical device uses 1 kilowatt of power for 1 hour, it uses 1 kilowatt-hour of energy.

It is important to remember that kW measures power, while kWh measures energy.

What Is a Calorie?

A calorie is a unit of energy.

The converter uses the thermochemical calorie.

One thermochemical calorie is equal to:

1 cal = 4.184 J

A kilocalorie is equal to 1,000 calories:

1 kcal = 4,184 J

Calories are commonly used when talking about the energy provided by food.

What Is an Electronvolt?

An electronvolt, or eV, is a very small unit of energy.

It is commonly used in physics, especially when working with particles, atoms, and very small amounts of energy.

One electronvolt is:

1 eV = 1.602176634 × 10⁻¹⁹ J

Because the value is extremely small, electronvolts are useful for measurements at the atomic and particle level.

What Is a BTU?

BTU means British Thermal Unit.

The converter uses the International Table BTU, shown as BTU (IT).

One BTU (IT) is equal to:

1 BTU = 1,055.056 J

BTU is often used to describe heat energy, especially in heating, cooling, and air-conditioning systems.

What Is a Foot-pound Force?

A foot-pound force, written as ft·lbf, is a unit of energy or work used mainly in the United States.

It describes the amount of work done when a force of one pound-force moves an object through a distance of one foot.

One foot-pound force is approximately:

1 ft·lbf = 1.355817948 J

This unit is also seen in mechanical and engineering applications.

What Is an Erg?

An erg is a small unit of energy from the centimetre-gram-second (CGS) system.

One erg is equal to:

1 erg = 0.0000001 J

This means:

10,000,000 erg = 1 J

The erg is mostly found in older scientific material and some specialized applications.

Difference Between Energy and Power

Energy and power are related, but they are not the same thing.

Energy is the ability to do work.

Power tells us how quickly energy is used or transferred.

Energy can be measured in:

• Joules
• Kilojoules
• Kilowatt-hours
• Calories
• BTU

Power can be measured in:

• Watts
• Kilowatts
• Megawatts

For example, a 1,000-watt device uses energy at a rate of 1,000 joules per second.

This is why watt (W) is a unit of power, while watt-hour (Wh) is a unit of energy.

Where Is Energy Used?

Energy is important in many areas.

Electricity

Electrical energy powers homes, computers, phones, machines, and other devices.

Food

Food provides chemical energy to the human body. Calories and kilocalories are commonly used to describe this energy.

Engineering

Engineers use energy measurements when designing machines, engines, and electrical systems.

Physics

Scientists use joules and electronvolts to measure energy in different physical systems.

Heating and Cooling

BTU is commonly used to describe heating and cooling capacity and thermal energy.

Mechanical Systems

Foot-pounds force can be used to describe mechanical work and energy.

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Why Use an Online Energy Converter?

Energy conversions can involve very large or very small numbers.

Doing these calculations manually can take time and can lead to mistakes.

Our online Energy Converter provides several benefits:

• Free to use: Convert energy values without paying.
• Fast results: Get your result in seconds.
• Easy to understand: No advanced math is required.
• Many units: Convert between 11 energy units.
• Useful for students: Practice energy conversions for school and college.
• Useful for engineers: Convert units used in technical calculations.
• Works online: Use the converter on a computer, tablet, or mobile phone.

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