Energy Converter

Enter the energy value you want to convert.

Select its original unit, such as J, kcal, kWh, or BTU.

View the equivalent values in all supported units.

Adjust decimal precision to control how many digits appear after the decimal point.

Use the swap control to reverse the selected units.

Copy an individual result using its copy control.

The equivalent values update as you change the input. You can use the results to compare measurements without calculating each conversion manually.

Convert energy units online with this free Energy Converter. Change joules, kilojoules, megajoules, calories, kilocalories, watt-hours, kilowatt-hours, BTU, foot-pounds, and electronvolts. Enter a value, select a unit, and view its equivalents across all supported units.

Use the converter to compare energy measurements in electricity, nutrition, heating, science, and mechanical work.

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

Different fields use different units to measure it. For example, electricity consumption is commonly measured in kilowatt-hours (kWh), food energy in kilocalories (kcal), and scientific measurements in joules (J) or electronvolts (eV).

This converter supports ten energy units:

The joule is the standard SI unit of energy. Other units can be converted to joules and then expressed in the unit you need.

The words calorie and Calorie can refer to different quantities.

Small calorie (cal): The energy needed to raise the temperature of 1 gram of water by approximately 1°C under a specified reference condition.

Kilocalorie (kcal): Equal to 1,000 small calories.

Food Calorie (Cal): In nutrition, a Calorie with a capital C usually means one kilocalorie.

Therefore:

1 kcal = 1,000 cal

1 food Calorie = 1 kcal

1 food Calorie ≈ 4,184 joules

For example, a food label showing 200 Calories generally means 200 kcal, not 200 small calories.

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

Energy measures the total amount of work or energy transferred.

Power measures how quickly energy is transferred or used.

Power is measured in watts (W), where 1 watt equals 1 joule per second. A watt-hour (Wh), on the other hand, is a unit of energy.

For example, a 100-watt appliance running for 2 hours uses 200 watt-hours (Wh) of energy. Its power remains 100 watts during that period.

This converter converts energy units. It does not convert power units such as watts or kilowatts.

Example 1: Electricity consumption

A 100-watt appliance operating for 2 hours uses:

100 W × 2 h = 200 Wh = 0.2 kWh

This is an energy measurement. The appliance's power rating is still 100 W.

Example 2: Food energy

A food serving labeled as containing 250 Calories provides approximately:

250 kcal

250,000 cal

1,046,000 J

1,046 kJ

Nutrition labels commonly use kilocalories, even when they display the word Calories.

Example 3: Heating energy

One kilowatt-hour is equivalent to approximately 3,412.14 BTU.

This conversion can help compare energy figures used in electricity and heating specifications. The exact BTU definition should be checked when working with technical standards that specify a particular BTU convention.

Example 4: Mechanical work

One foot-pound (ft·lbf) is approximately 1.35582 joules. This unit is used to describe mechanical work, such as the work involved in lifting or moving an object.

Example 5: Scientific energy

One electronvolt (eV) is approximately 1.60218 × 10⁻¹⁹ joules. Electronvolts are useful for describing very small energy quantities in atomic and particle physics.

An energy converter can help you:

Convert electricity measurements between Wh, kWh, and joules.

Compare food energy expressed in Calories, kcal, and kJ.

Understand heating values measured in BTU.

Convert mechanical work between foot-pounds and joules.

Compare scientific energy values expressed in electronvolts and joules.