Converter category
Energy & Work Converter
Convert between joules, kilojoules, megajoules, calories, kilocalories, watt-hours, kilowatt-hours, BTU, therms, foot-pounds, electronvolts, ergs, tons of TNT, barrels of oil equivalent, and many other energy units.
Universal Energy & Work Converter
About energy & work conversions
Energy conversions are used in nutrition, fitness, physics, engineering, electricity billing, and heating and cooling. Our energy converter covers SI units such as joules and kilojoules, nutritional units including calories and kilocalories, electrical units such as watt-hours and kilowatt-hours, and thermal units like British thermal units and therms. It also includes scientific units like electronvolts and atomic units. Every conversion uses defined physical relationships, so you can compare food labels, electricity bills, workout data, and scientific measurements with confidence.
Most popular energy & work conversions
Available units
Popular energy & work conversions (2862 total)
Unit definitions
Joule (J)
A joule is the SI unit of energy, equal to the work done by a force of one newton over one meter.
Origin: Named after James Prescott Joule, who studied the mechanical equivalent of heat.
Current use: Physics, Engineering, Energy measurement
Kilojoule (kJ)
A kilojoule is 1000 joules. Food labels often show energy in kilojoules.
Origin: Metric prefix kilo- means one thousand.
Current use: Food labeling (outside US), Chemistry, Engineering
Megajoule (MJ)
A megajoule is one million joules, about the kinetic energy of a car at highway speed.
Origin: Metric prefix mega- means one million.
Current use: Engineering, Physics, Energy systems
Calorie (cal)
A calorie is the energy to raise 1 gram of water by 1°C. Used for food energy.
Origin: From Latin calor meaning heat. Defined in 1824.
Current use: Food labeling, Chemistry, Biology
Kilocalorie (kcal)
A kilocalorie (Calorie with capital C) is 1000 calories, used for food energy. 1 kcal = 4.184 kJ.
Origin: Also called a food calorie. Used in nutrition labeling worldwide except US.
Current use: Nutrition, Dietary planning, Food science
Watt-hour (Wh)
A watt-hour is the energy of one watt sustained for one hour. 1 Wh = 3600 J.
Origin: Named after James Watt, inventor of the steam engine.
Current use: Battery capacity, Electrical billing, Power measurement
Kilowatt-hour (kWh)
A kilowatt-hour is the standard unit of electricity billing. 1 kWh = 3.6 MJ.
Origin: Standard unit for residential and commercial electricity.
Current use: Electricity billing, Energy consumption, Solar systems
BTU (BTU)
A BTU is the energy to raise 1 pound of water by 1°F. 1 BTU ≈ 1055 J.
Origin: Defined in 1876 as the energy needed to raise water temperature.
Current use: HVAC systems, Appliance rating, Natural gas
Therm (thm)
A therm is 100,000 BTU, the standard unit for natural gas billing in the US.
Origin: From Greek therme meaning heat.
Current use: Natural gas billing, Heating systems, Energy industry
Foot-pound (ft·lb)
A foot-pound is the work to raise 1 pound by 1 foot. 1 ft·lb ≈ 1.36 J.
Origin: Imperial unit of energy and torque.
Current use: Torque measurement, Mechanical engineering, American machinery
Electronvolt (eV)
An electronvolt is the energy gained by an electron moving through 1 volt. 1 eV = 1.6×10⁻¹⁹ J.
Origin: Used in atomic and particle physics.
Current use: Particle physics, Semiconductors, Atomic physics
Erg (erg)
An erg is the CGS unit of energy, the work by a force of 1 dyne over 1 cm.
Origin: From Greek ergon meaning work. CGS system unit.
Current use: Physics, Small-scale mechanics, Historical use
Ton of TNT (t TNT)
A ton of TNT is the energy released by burning 1 ton of TNT, about 4.184 GJ.
Origin: Standard unit for measuring explosive energy.
Current use: Explosives, Military, Mining
Barrel of Oil Equivalent (BOE)
BOE represents the energy in one barrel (42 US gallons) of crude oil, about 6.1 GJ.
Origin: Standard in oil and gas industry for comparing energy sources.
Current use: Oil industry, Energy comparison, Resource estimation
Gigajoule (GJ)
1 billion joules. Large energy unit.
Origin: SI prefix giga- = 10^9.
Current use: Power generation, Large facilities, Industrial
Millijoule (mJ)
One thousandth of a joule.
Origin: SI prefix milli- = 0.001.
Current use: Medical lasers, Small electronics, Research
Microjoule (µJ)
One millionth of a joule.
Origin: SI prefix micro- = 10^-6.
Current use: Particle accelerators, Research, Quantum
Nanojoule (nJ)
One billionth of a joule.
Origin: SI prefix nano- = 10^-9.
Current use: Nanotechnology, Biophysics, Research
Hartree (Atomic Unit) (E_h)
Atomic unit of energy ≈ 27.2 eV.
Origin: Named after Douglas Hartree.
Current use: Quantum mechanics, Atomic physics, Computational chemistry
Rydberg (Ry)
Photon energy to ionize hydrogen ≈ 13.6 eV.
Origin: Named after Johannes Rydberg.
Current use: Spectroscopy, Atomic physics, Quantum
Gigawatt Hour (GWh)
1 billion watt-hours. Large-scale electricity.
Origin: Power generation standard.
Current use: Power plants, Grid electricity, Large facilities
Megawatt Hour (MWh)
1 million watt-hours. Industrial electricity.
Origin: Commercial electricity standard.
Current use: Industrial plants, Data centers, Large buildings
Kilowatt Second (kW·s)
1 kilowatt for 1 second = 1000 J.
Origin: Energy unit.
Current use: Electrical, Physics, Engineering
Watt Second (W·s)
Same as joule. SI energy unit.
Origin: Named after James Watt.
Current use: Physics, Electrical, General use
Newton Meter (N·m)
Same as joule. SI energy unit.
Origin: Work/energy equivalence.
Current use: Mechanics, Physics, Engineering
Horsepower Hour (hph)
Energy from 1 hp over 1 hour.
Origin: Mechanical equivalent.
Current use: US machinery, Engine energy, Historical
Metric Horsepower Hour (hph metric)
Energy from 1 metric hp over 1 hour.
Origin: European standard.
Current use: European machinery, German engineering
Kilocalorie (IT) (kcal_IT)
International Table calorie = 4.1868 J.
Origin: IT standard.
Current use: Food labeling (intl), Chemistry, Research
Kilocalorie (Th) (kcal_th)
Thermochemical calorie = 4.184 J.
Origin: Thermodynamics standard.
Current use: Thermodynamics, Chemistry, Food science
Calorie (IT) (cal_IT)
Heat to raise 1g water by 1°C (IT).
Origin: Established 1929.
Current use: Food science, Chemistry, Biology
Calorie (Th) (cal_th)
Thermochemical calorie = 4.184 J exact.
Origin: Thermodynamics.
Current use: Thermodynamics, Chemical engineering
MBTU (MBTU)
1000 BTU. US natural gas standard.
Origin: HVAC industry.
Current use: Natural gas, HVAC, US energy
Ton Hour (Refrigeration) (ton·hr)
Cooling energy over 1 hour.
Origin: Refrigeration industry.
Current use: Refrigeration, AC systems, Cold storage
Foe (Kilotons) (foe)
10^27 ergs = 4.184×10^14 J.
Origin: Astronomy unit.
Current use: Supernovae, Astronomy, Star energy
Foe (Barrels) (foe bbl)
Energy in 10 billion barrels of oil.
Origin: Oil industry comparison.
Current use: Energy comparison, Oil industry
Gigaton TNT (Gt)
Billion tons TNT. Nuclear weapon scale.
Origin: Nuclear weapons standard.
Current use: Nuclear weapons, Asteroid impacts, Climate
Megaton TNT (Mt)
Million tons TNT.
Origin: Nuclear weapons.
Current use: Nuclear weapons, Energy comparison
Kiloton TNT (kt)
Thousand tons TNT.
Origin: Nuclear weapons.
Current use: Nuclear yield, Explosives
Ton (Explosive) (t)
TNT equivalent = 4.184 GJ.
Origin: Explosives standard.
Current use: Explosives, Mining, Demolition
Dyne Centimeter (dyn·cm)
CGS energy = 1 erg = 0.1 µJ.
Origin: CGS system.
Current use: Physics, CGS system, Small energies
Gram-force Meter (gf·m)
Small energy unit.
Origin: Gravity work.
Current use: Small mechanics, Labs
Gram-force Centimeter (gf·cm)
Very small energy.
Origin: CGS energy.
Current use: Microphysics, Labs
Kilogram-force Centimeter (kgf·cm)
Small mechanical energy.
Origin: Engineering.
Current use: Small mechanisms, Springs
Kilogram-force Meter (kgf·m)
Lift 1 kg by 1 m = 9.8 J.
Origin: Classical mechanics.
Current use: Mechanics, Engineering, Education
Kilopond Meter (kp·m)
Same as kgf-m. European.
Origin: German engineering.
Current use: European machinery, Classical physics
Pound-force Foot (lbf·ft)
US mechanical energy = 1.356 J.
Origin: Imperial mechanics.
Current use: US machinery, Torque, Engines
Pound-force Inch (lbf·in)
Small US energy = 0.113 J.
Origin: Imperial small work.
Current use: Small US mechanisms, Precision
Ounce-force Inch (ozf·in)
Very small US energy.
Origin: Small Imperial work.
Current use: Model aircraft, RC, Small springs
Foot Pound (ft·lbf)
Same as lbfft. Imperial energy.
Origin: US classical.
Current use: US mechanics, Engines, Machinery
Inch Pound (in·lbf)
Same as lbf-in.
Origin: Imperial small work.
Current use: US small mechanisms, Fasteners
Inch Ounce (in·ozf)
Very small Imperial energy.
Origin: Small mechanical work.
Current use: Precision mechanics, Watches, Micro
Poundal Foot (pdl·ft)
FPS energy = 0.042 J.
Origin: Foot-pound-second system.
Current use: US physics, Education
Therm (EC) (thm_EC)
100,000 BTU (EC). European gas.
Origin: EU gas standard.
Current use: European gas, Heating, Energy
Therm (US) (thm_US)
100,000 BTU (US). US gas.
Origin: US gas standard.
Current use: US natural gas, Heating, US energy
Common uses for energy conversions
Energy conversions are used for nutrition labels, fitness tracking, electricity bills, heating and cooling, physics homework, engineering, and fuel comparisons.
Frequently asked questions about energy & work
How many joules are in 1 calorie?+
One nutritional calorie (kilocalorie) is about 4,184 joules. One small calorie is about 4.184 joules.
What is the difference between a calorie and a kilocalorie?+
A kilocalorie equals 1,000 calories. Food labels in many countries show kilocalories but call them Calories with a capital C.
Which energy units does this converter support?+
It supports SI, nutritional, electrical, thermal, and scientific energy units — over 15 in total.