Energy Conversion Calculator

Energy Unit Converter

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About Energy

Energy is the capacity to do work or produce heat. It comes in many forms, such as kinetic, potential, thermal, electrical, chemical, nuclear, and more. The standard unit of energy in the International System of Units (SI) is the joule (J).

Energy is conserved in isolated systems according to the First Law of Thermodynamics, meaning it can neither be created nor destroyed, only converted from one form to another.

Various disciplines use different units of energy:

Physics: Joules (J), electron volts (eV)
Nutrition: Calories (cal), kilocalories (kcal)
Electricity: Watt-hours (Wh), kilowatt-hours (kWh)
Heating and Cooling: British Thermal Units (BTU)
Nuclear Physics: Megaelectron volts (MeV)

+ Learn More About Energy Units

SI Units

Joule (J): The SI unit of energy, equal to the energy transferred when a force of one newton acts on an object over a distance of one meter.

Kilojoule (kJ): 1,000 joules, commonly used in thermodynamics and nutrition.

Megajoule (MJ): 1,000,000 joules, used for larger energy quantities.

Calories

Calorie (cal): The energy needed to raise the temperature of 1 gram of water by 1°C (from 14.5°C to 15.5°C) at standard atmospheric pressure.

Kilocalorie (kcal): 1,000 calories. This is what's commonly referred to as a "Calorie" (with a capital C) in nutrition.

Electrical Units

Watt-hour (Wh): The energy equivalent to a power of one watt sustained for one hour.

Kilowatt-hour (kWh): 1,000 watt-hours, the unit used in electrical billing.

Scientific Units

Electron Volt (eV): The energy gained by an electron moving across an electric potential difference of one volt. Used in atomic and nuclear physics.

Erg: A CGS unit of energy, equal to 10^-7 joules.

Conversion Factors

Key conversion factors between common energy units:

1 calorie = 4.184 joules
1 kilowatt-hour = 3,600,000 joules (3.6 MJ)
1 BTU = 1,055 joules
1 electron volt = 1.602 × 10^-19 joules
1 ton of TNT = 4.184 × 10^9 joules (4.184 GJ)

Energy in Daily Life

Energy is fundamental to all aspects of daily life:

Human Energy: Adults typically consume about 2,000-2,500 kilocalories (kcal) per day from food.
Household Energy: An average U.S. home uses about 30 kilowatt-hours (kWh) of electricity daily.
Transportation Energy: A gallon of gasoline contains about 33.7 kilowatt-hours (kWh) of energy.
Global Energy: The world consumes over 170,000 terawatt-hours of primary energy annually.