Energy Converter

Energy is the capacity to do work or to heat something. Its SI unit is the joule (J), the work done by a force of one newton over one meter. Electricity is billed in kilowatt-hours (kWh), heating and cooling in Btu, food in kilocalories, and atomic physics in electron-volts.

Energy is power times time, so a 2,000 W heater running for 3 hours uses 2 kW × 3 h = 6 kWh.

How to convert energy units

Type a value into any field, and every other unit is calculated at once. For example, 6 kWh:

1. In megajoules: multiply by 3.6, since 1 kWh is 3,600,000 J.

   6 × 3.6 = 21.6 MJ

2. In Btu: multiply by 3,412.14.

   6 × 3,412.14 = 20,473 Btu

Food calories are kilocalories. The "Calorie" on a food label is 1,000 of the calories in this converter, so enter it times 1,000: a 250 kcal snack is 250,000 cal, or 1,047 kJ.

Common conversions

Energy units

• Joule (J): The joule is the SI unit of energy, defined as the amount of work done by a force of one newton moving through a distance of one meter.

• Kilojoule (kJ): The kilojoule is a metric unit of energy equal to one thousand joules.
  Conversion factor: 1 kJ = 1,000 J

• Megajoule (MJ): The megajoule is a metric unit of energy equal to one million joules.
  Conversion factor: 1 MJ = 1,000,000 J

• Watt-second (Ws): The watt-second is a unit of energy that is equivalent to 1 joule. It is the energy equivalent to the power of one watt sustained for one second.
  Conversion factor: 1 Ws = 1 J

• Watt-hour (Wh): The watt-hour is a unit of energy equal to one watt of power consumed for one hour.
  Conversion factor: 1 Wh = 3,600 Ws = 3,600 J

• Kilowatt-hour (kWh): The kilowatt-hour is a unit of energy commonly used to measure electricity consumption. It represents the energy consumption of a device operating at a power of one kilowatt for one hour.
  Conversion factor: 1 kWh = 1,000 Wh = 3,600,000 Ws = 3,600,000 J

• Calorie (cal): The calorie is a unit of energy used commonly around the world. For historical reasons, two main definitions of "calorie" are in wide use. The large calorie, food calorie, or kilogram calorie is defined as the amount of heat needed to raise the temperature of one kilogram of water by one degree Celsius. The small calorie or gram calorie is defined as the amount of heat needed to cause the same increase in one gram of water. Thus, 1 large calorie is equal to 1000 small calories. The calorie unit in this energy converter refers to small calories.
  Conversion factor: 1 cal (IT) = 4.1868 J; 1 cal (th) = 4.184 J

• Btu (btu): The British Thermal Unit is a unit of energy commonly used in the United States. It is defined as the amount of heat required to raise the temperature of one pound of water by one degree Fahrenheit at a constant pressure of one atmosphere.
  Conversion factor: 1 Btu (IT) = 1,055.06 J; 1 Btu (th) = 1,054.35 J

• Ton (explosives): The ton of explosives is a unit of energy often used in mining and explosives engineering. It refers to the energy release equivalent to one ton of TNT (Trinitrotoluene).
  Conversion factor: 1 ton (explosives) = 4.184 GJ (gigajoules)

• Kilogram-force meter (kgf•m): The kilogram-force meter is a unit derived from the force exerted by a kilogram-force acting over a distance of one meter.
  Conversion factor: 1 kgf•m = 9.80665 J

• Pound-force foot (lbf•ft): The pound-force foot is a unit derived from the force exerted by a pound-force acting over a distance of one foot.
  Conversion factor: 1 lbf•ft = 1.35582 J

• Poundal foot (pdl•ft): The poundal foot is a unit derived from the force exerted by a poundal acting over a distance of one foot.
  Conversion factor: 1 pdl•ft = 0.0421401 J

• Erg (erg): The erg is a unit of energy commonly used in the field of atomic and molecular physics. It is equal to one dyne (a unit of force) acting over a distance of one centimeter.
  Conversion factor: 1 erg = 0.0000001 J

• Electron-volt (eV): The electron-volt is a unit of energy often used in atomic and particle physics. It represents the amount of energy gained by an electron when accelerated through an electric potential difference of one volt.
  Conversion factor: 1 eV = 1.60218 * 10^(−19) J

Difference between "IT" and "th" units

• "IT" (International Table)
  The "IT" in energy units stands for "International Table". It is a reference point based on the International Steam Table calorie. The International Table calorie (cal IT) is defined as exactly 4.1868 joules. Energy units like BTU IT (British Thermal Unit, International Table) and Calorie IT (International Table Calorie) are based on this reference point.

• "th" (Thermochemical)
  The "th" in energy units stands for "thermochemical". It is a reference point based on the Thermochemical Calorie. The Thermochemical Calorie (cal th) is defined as exactly 4.184 joules. Energy units like BTU th (British Thermal Unit, Thermochemical) and Calorie th (Thermochemical Calorie) are based on this reference point.

The IT units are about 0.07% larger than the thermochemical ones, so the difference matters only in precise work.