Energy Converter

• Joules to Calories1 J = 0.239006 cal
• Calories to Joules1 cal = 4.184 J
• Joules to Kilojoules1 J = 0.001 kJ
• Joules to Megajoules1 J = 1e-6 MJ
• Joules to Kilocalories1 J = 0.000239006 kcal
• Joules to Watt Hours1 J = 0.000277778 Wh
• Joules to Kilowatt Hours1 J = 2.7778e-7 kWh
• Joules to Electron Volts1 J = 6.2415e+18 eV
• Joules to British Thermal Units1 J = 0.000947813 BTU
• Joules to Foot Pounds1 J = 0.737562 ft⋅lb
• Joules to Therms1 J = 9.4782e-9 thm
• Joules to Horsepower Hours1 J = 3.7251e-7 hp⋅h

All 23 energy units are converted through a single base unit, so any unit can be converted to any other. Enter a value, choose the units and press Convert, or open a conversion page for the exact factor and a reference table.

For example, 1 joules (J) = 0.239006 calories (cal).

Joules (J)

The joule is the SI unit of energy: the work done by a force of one newton over one meter. Lifting a small apple one meter takes about one joule.

Kilojoules (kJ)

A kilojoule is 1,000 joules. Food energy is labelled in kilojoules in many countries; 1 kJ is about 0.239 kilocalories.

Megajoules (MJ)

A megajoule is one million joules. A kilowatt-hour is 3.6 MJ, and vehicle fuels contain roughly 30 to 45 MJ per liter or kilogram.

Calories (cal)

The calorie used here is the thermochemical calorie, exactly 4.184 joules, roughly the energy needed to warm one gram of water by one degree Celsius. Food calories are actually kilocalories.

Kilocalories (kcal)

A kilocalorie is 1,000 calories, or 4,184 joules. It is the Calorie written with a capital C on food labels and in diet guidance.

Watt Hours (Wh)

A watt-hour is the energy of one watt sustained for one hour, exactly 3,600 joules. Phone and laptop batteries are rated in watt-hours.

Kilowatt Hours (kWh)

A kilowatt-hour is 1,000 watt-hours, exactly 3.6 megajoules. Household electricity is billed per kWh.

Electron Volts (eV)

An electronvolt is the energy an electron gains when accelerated through one volt, exactly 1.602176634 × 10⁻¹⁹ joules. Particle and photon energies are quoted in eV.

British Thermal Units (BTU)

A British thermal unit is the energy needed to raise one pound of water by one degree Fahrenheit, about 1,055 joules. Heating and air-conditioning capacities are rated in BTU per hour.

Therms (thm)

A therm is 100,000 BTU, about 105.5 megajoules. Natural gas is billed in therms in the United States.

Foot Pounds (ft⋅lb)

A foot-pound is the work done by a force of one pound-force acting through one foot, about 1.356 joules. The same name is also used for torque.

Horsepower Hours (hp⋅h)

A horsepower-hour is one horsepower sustained for one hour, about 2.685 megajoules.

Tons Tnt (tTNT)

A ton of TNT is a conventional energy unit equal to 4.184 gigajoules, used for explosions and the yield of nuclear weapons.

• PressurePascals, bar, psi and more.
• ForceNewtons, pound-force, dynes and more.
• TorqueNewton-meters, pound-feet and more.
• AccelerationMeters per second squared, g-force and more.
• DensityKilograms per cubic meter, g/cm³ and more.