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Smart Energy Conversion

Energy Unit Converter

Convert energy measurements between joules, kilojoules, kilowatt-hours, calories, BTU, electronvolts and many other units with fast and accurate results.

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16 Energy Units
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Energy unit conversion illustration Illustration showing stored energy flowing between joules and kilowatt-hours. SI ENERGY J ELECTRICAL kWh SCIENCE J • kJ • MJ ELECTRICITY Wh • kWh THERMAL cal • BTU
J SI Energy Unit
kWh Electrical Energy
BTU Thermal Energy

Convert Energy Units Instantly

Enter an energy value and select any two supported units to get an instant conversion.

Energy Unit Converter Scientific, electrical and thermal units
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Conversion Result
0.0000002778 kWh
1 J = 0.0000002778 kWh
Quick values

Popular Energy Conversions

Quickly load frequently used scientific, electrical and thermal energy conversions.

kWh to Joules 1 kWh = 3,600,000 J
Joules to kWh 3.6 MJ = 1 kWh
Calories to Joules 1 cal = 4.184 J
BTU to Joules 1 BTU ≈ 1,055.06 J
Watt-hours to Joules 1 Wh = 3,600 J
kcal to Joules 1 kcal = 4,184 J

Why Use Our Energy Unit Converter?

Convert energy measurements without manually remembering conversion factors or performing repetitive calculations.

Instant Results

Results update automatically whenever you enter a value or change either energy unit.

Accurate Factors

Standard conversion factors are used for scientific, electrical and thermal energy units.

Multiple Categories

Convert joules, watt-hours, calories, BTU, electronvolts, therms and larger energy units.

Free & Private

All calculations run directly in your browser without an account or registration.

What Is Energy?

Energy is the capacity to perform work or cause change. It appears in many forms, including mechanical, electrical, thermal, chemical and radiant energy.

The joule (J) is the SI unit of energy. Different industries and scientific fields, however, often use other units such as kilowatt-hours, calories and BTUs.

What is a Joule?

A joule is the standard SI unit used to measure energy and work. Larger energy quantities may be expressed in kilojoules, megajoules or gigajoules.

Energy vs Power

Energy represents a total quantity, while power describes how quickly energy is transferred or used. A kilowatt is a unit of power, whereas a kilowatt-hour is a unit of energy.

USEFUL ENERGY RELATIONSHIPS
1 kWh = 3.6 MJ
Kilowatt-hours measure energy, not instantaneous power. One kilowatt used continuously for one hour equals one kilowatt-hour of energy.
1 Wh 3,600 J
1 kWh 3,600,000 J
1 calorie 4.184 J
1 kcal 4,184 J
1 BTU ≈ 1,055.06 J

Common Energy Units

Use this reference table to compare common energy units with their equivalent value in joules.

Energy Unit Symbol Equivalent in Joules
Joule J 1 J
Kilojoule kJ 1,000 J
Megajoule MJ 1,000,000 J
Watt-hour Wh 3,600 J
Kilowatt-hour kWh 3,600,000 J
Calorie cal 4.184 J
Kilocalorie kcal 4,184 J
British Thermal Unit BTU ≈ 1,055.06 J
Foot-pound Force ft·lbf ≈ 1.35582 J
Electronvolt eV 1.602176634 × 10⁻¹⁹ J

Where Are Energy Conversions Used?

Energy conversions are useful across electricity, physics, heating, food science, batteries and engineering.

Electricity Usage

Convert watt-hours and kilowatt-hours when working with electricity consumption and energy storage.

Solar & Batteries

Compare stored and generated energy values for batteries, solar systems and renewable energy projects.

Heating & HVAC

Convert between joules, BTUs and other thermal energy measurements used in heating systems.

Physics & Science

Convert joules, electronvolts and related units for scientific calculations and education.

Food Energy

Compare calories, kilocalories and joules when working with food energy measurements.

Engineering

Convert large energy quantities for machinery, fuels, industrial processes and technical calculations.

How to Use the Energy Unit Converter

Get your energy conversion in three simple steps.

1

Enter Energy Value

Type the energy measurement you want to convert into the input field.

2

Select Energy Units

Choose your current energy unit and then select the unit you want as the result.

3

View Instant Result

The converted value and one-unit conversion relationship appear automatically.

Energy Unit Converter FAQs

Common questions about joules, kilowatt-hours, calories, BTUs and energy conversions.

The SI unit of energy is the joule, represented by the symbol J. Joules are widely used in physics, engineering and scientific calculations.
One kilowatt-hour is equal to exactly 3,600,000 joules, which is also equal to 3.6 megajoules.
One thermochemical calorie is equal to 4.184 joules.
In nutrition, a capital-C Calorie usually means one kilocalorie, which equals 1,000 small calories or 4,184 joules.
A kilowatt (kW) measures power, while a kilowatt-hour (kWh) measures energy. For example, a 1 kW device operating for one hour uses 1 kWh of energy.
Yes. Select BTU as the source unit and kilowatt-hour as the target unit. The converter will calculate the equivalent energy value automatically.
An electronvolt is a very small unit of energy commonly used in atomic, nuclear and particle physics. One electronvolt equals 1.602176634 × 10⁻¹⁹ joules.
Yes. This Energy Unit Converter is free to use and performs all conversions directly in your browser without requiring registration.