What is the difference between joules and calories?

A joule is the SI unit of energy, while a calorie (or kilocalorie in nutrition) is an older unit. 1 kilocalorie equals 4,186.8 joules. Food energy is typically measured in kilocalories (often labeled as "Calories" with a capital C).

How much energy does 1 kWh represent?

1 kilowatt-hour equals 3.6 million joules or 3,600 kilojoules. This is the amount of energy consumed when a 1,000-watt device runs for one hour.

Energy Converter

Convert energy measurements between joules, calories, BTU, kilowatt-hours, and more.

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Popular Energy Conversions

J to kJ kJ to kcal (IT)kWh to MJ BTU (IT) to kJ kWh to therm (US)

Complete List of Energy Units for Conversion

1 Kilojoule [kJ] = 1000.00 Joule [J]

Kilojoule to Joule, Joule to Kilojoule

1 Megajoule [MJ] = 1.00000e+6 Joule [J]

Megajoule to Joule, Joule to Megajoule

1 Gigajoule [GJ] = 1.00000e+9 Joule [J]

Gigajoule to Joule, Joule to Gigajoule

1 Terajoule [TJ] = 1.00000e+12 Joule [J]

Terajoule to Joule, Joule to Terajoule

1 Petajoule [PJ] = 1.00000e+15 Joule [J]

Petajoule to Joule, Joule to Petajoule

1 Exajoule [EJ] = 1.00000e+18 Joule [J]

Exajoule to Joule, Joule to Exajoule

1 Watt-second [W·s] = 1.00000 Joule [J]

Watt-second to Joule, Joule to Watt-second

1 Watt-hour [Wh] = 3600.00 Joule [J]

Watt-hour to Joule, Joule to Watt-hour

1 Kilowatt-hour [kWh] = 3.60000e+6 Joule [J]

Kilowatt-hour to Joule, Joule to Kilowatt-hour

1 Megawatt-hour [MWh] = 3.60000e+9 Joule [J]

Megawatt-hour to Joule, Joule to Megawatt-hour

1 Gigawatt-hour [GWh] = 3.60000e+12 Joule [J]

Gigawatt-hour to Joule, Joule to Gigawatt-hour

1 Electronvolt [eV] = 1.60218e-19 Joule [J]

Electronvolt to Joule, Joule to Electronvolt

1 Kiloelectronvolt [keV] = 1.60218e-16 Joule [J]

Kiloelectronvolt to Joule, Joule to Kiloelectronvolt

1 Megaelectronvolt [MeV] = 1.60218e-13 Joule [J]

Megaelectronvolt to Joule, Joule to Megaelectronvolt

1 British Thermal Unit (IT) [BTU (IT)] = 1055.06 Joule [J]

British Thermal Unit (IT) to Joule, Joule to British Thermal Unit (IT)

1 British Thermal Unit (th) [BTU (th)] = 1054.35 Joule [J]

British Thermal Unit (th) to Joule, Joule to British Thermal Unit (th)

1 Therm (US) [therm (US)] = 1.05480e+8 Joule [J]

Therm (US) to Joule, Joule to Therm (US)

1 Therm (EC) [therm (EC)] = 1.05506e+8 Joule [J]

Therm (EC) to Joule, Joule to Therm (EC)

1 Ton of TNT [t TNT] = 4.18400e+9 Joule [J]

Ton of TNT to Joule, Joule to Ton of TNT

1 Quad (10¹⁵ BTU) [quad] = 1.05506e+18 Joule [J]

Quad (10¹⁵ BTU) to Joule, Joule to Quad (10¹⁵ BTU)

1 Calorie (IT) [cal (IT)] = 4.18680 Joule [J]

Calorie (IT) to Joule, Joule to Calorie (IT)

1 Calorie (th) [cal (th)] = 4.18400 Joule [J]

Calorie (th) to Joule, Joule to Calorie (th)

1 Kilocalorie (IT) [kcal (IT)] = 4186.80 Joule [J]

Kilocalorie (IT) to Joule, Joule to Kilocalorie (IT)

1 Kilocalorie (th) [kcal (th)] = 4184.00 Joule [J]

Kilocalorie (th) to Joule, Joule to Kilocalorie (th)

1 Calorie (mean) [cal (mean)] = 4.19002 Joule [J]

Calorie (mean) to Joule, Joule to Calorie (mean)

1 Kilocalorie (mean) [kcal (mean)] = 4190.02 Joule [J]

Kilocalorie (mean) to Joule, Joule to Kilocalorie (mean)

1 Foot-Pound Force [ft·lbf] = 1.35582 Joule [J]

Foot-Pound Force to Joule, Joule to Foot-Pound Force

1 Inch-Pound Force [in·lbf] = 0.112985 Joule [J]

Inch-Pound Force to Joule, Joule to Inch-Pound Force

1 Erg [erg] = 1.00000e-7 Joule [J]

Erg to Joule, Joule to Erg

1 Kilogram-meter [kg·m] = 9.80665 Joule [J]

Kilogram-meter to Joule, Joule to Kilogram-meter

1 Kilowatt-hour (thermal) [kWh(th)] = 3412.14 Joule [J]

Kilowatt-hour (thermal) to Joule, Joule to Kilowatt-hour (thermal)

Understanding energy units

The joule (J) is the SI unit of energy, defined as the amount of work done when a force of one newton acts through a distance of one meter. Energy measures the capacity to perform work or produce heat.

Common energy relationships

1 joule = 1 newton-meter (N·m)
1 kilocalorie = 4,186.8 joules
1 BTU (British Thermal Unit) ≈ 1,055.06 joules
1 kilowatt-hour (kWh) = 3,600,000 joules
1 electronvolt (eV) ≈ 1.602 × 10⁻¹⁹ joules

Common energy applications

Joules are used in physics and engineering for scientific calculations. Calories are used in nutrition to describe food energy content (where 1 food calorie = 1 kilocalorie). Kilowatt-hours are used to measure electricity consumption. BTUs are used in HVAC systems and heating applications. Electronvolts are used in atomic and nuclear physics.

Energy conversion accuracy

Energy conversions use exact relationships defined by the International System of Units and NIST standards. The conversion factors are based on fundamental definitions of work, power, and the joule.

Frequently Asked Questions

What is the difference between joules and calories?: A joule is the SI unit of energy, while a calorie (or kilocalorie in nutrition) is an older unit. 1 kilocalorie equals 4,186.8 joules. Food energy is typically measured in kilocalories (often labeled as "Calories" with a capital C).
How much energy does 1 kWh represent?: 1 kilowatt-hour equals 3.6 million joules or 3,600 kilojoules. This is the amount of energy consumed when a 1,000-watt device runs for one hour.

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Common Unit Systems