Energy Converter

Convert between all common energy units including joules, kilojoules, calories, kilocalories, watt-hours, kilowatt-hours, BTU, electron volts, and ergs.

Energy Converter 13 units
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Common Energy Conversions

All Energy Conversions

Browse all unit combinations — each page has a dedicated converter and conversion table.

Joules → Kilojoules Joules → Megajoules Joules → Gigajoules Joules → Calories Joules → Kilocalories Joules → Watt-hours Joules → Kilowatt-hours Joules → Megawatt-hours Joules → BTU Joules → Electronvolts Joules → Ergs Joules → Foot-pounds Kilojoules → Joules Kilojoules → Megajoules Kilojoules → Gigajoules Kilojoules → Calories Kilojoules → Kilocalories Kilojoules → Watt-hours Kilojoules → Kilowatt-hours Kilojoules → Megawatt-hours Kilojoules → BTU Kilojoules → Electronvolts Kilojoules → Ergs Kilojoules → Foot-pounds Megajoules → Joules Megajoules → Kilojoules Megajoules → Gigajoules Megajoules → Calories Megajoules → Kilocalories Megajoules → Watt-hours Megajoules → Kilowatt-hours Megajoules → Megawatt-hours Megajoules → BTU Megajoules → Electronvolts Megajoules → Ergs Megajoules → Foot-pounds Gigajoules → Joules Gigajoules → Kilojoules Gigajoules → Megajoules Gigajoules → Calories Gigajoules → Kilocalories Gigajoules → Watt-hours Gigajoules → Kilowatt-hours Gigajoules → Megawatt-hours Gigajoules → BTU Gigajoules → Electronvolts Gigajoules → Ergs Gigajoules → Foot-pounds Calories → Joules Calories → Kilojoules Calories → Megajoules Calories → Gigajoules Calories → Kilocalories Calories → Watt-hours Calories → Kilowatt-hours Calories → Megawatt-hours Calories → BTU Calories → Electronvolts Calories → Ergs Calories → Foot-pounds Kilocalories → Joules Kilocalories → Kilojoules Kilocalories → Megajoules Kilocalories → Gigajoules Kilocalories → Calories Kilocalories → Watt-hours Kilocalories → Kilowatt-hours Kilocalories → Megawatt-hours Kilocalories → BTU Kilocalories → Electronvolts Kilocalories → Ergs Kilocalories → Foot-pounds Watt-hours → Joules Watt-hours → Kilojoules Watt-hours → Megajoules Watt-hours → Gigajoules Watt-hours → Calories Watt-hours → Kilocalories Watt-hours → Kilowatt-hours Watt-hours → Megawatt-hours Watt-hours → BTU Watt-hours → Electronvolts Watt-hours → Ergs Watt-hours → Foot-pounds Kilowatt-hours → Joules Kilowatt-hours → Kilojoules Kilowatt-hours → Megajoules Kilowatt-hours → Gigajoules Kilowatt-hours → Calories Kilowatt-hours → Kilocalories Kilowatt-hours → Watt-hours Kilowatt-hours → Megawatt-hours Kilowatt-hours → BTU Kilowatt-hours → Electronvolts Kilowatt-hours → Ergs Kilowatt-hours → Foot-pounds Megawatt-hours → Joules Megawatt-hours → Kilojoules Megawatt-hours → Megajoules Megawatt-hours → Gigajoules Megawatt-hours → Calories Megawatt-hours → Kilocalories Megawatt-hours → Watt-hours Megawatt-hours → Kilowatt-hours Megawatt-hours → BTU Megawatt-hours → Electronvolts Megawatt-hours → Ergs Megawatt-hours → Foot-pounds BTU → Joules BTU → Kilojoules BTU → Megajoules BTU → Gigajoules BTU → Calories BTU → Kilocalories BTU → Watt-hours BTU → Kilowatt-hours BTU → Megawatt-hours BTU → Electronvolts BTU → Ergs BTU → Foot-pounds Electronvolts → Joules Electronvolts → Kilojoules Electronvolts → Megajoules Electronvolts → Gigajoules Electronvolts → Calories Electronvolts → Kilocalories Electronvolts → Watt-hours Electronvolts → Kilowatt-hours Electronvolts → Megawatt-hours Electronvolts → BTU Electronvolts → Ergs Electronvolts → Foot-pounds Ergs → Joules Ergs → Kilojoules Ergs → Megajoules Ergs → Gigajoules Ergs → Calories Ergs → Kilocalories Ergs → Watt-hours Ergs → Kilowatt-hours Ergs → Megawatt-hours Ergs → BTU Ergs → Electronvolts Ergs → Foot-pounds Foot-pounds → Joules Foot-pounds → Kilojoules Foot-pounds → Megajoules Foot-pounds → Gigajoules Foot-pounds → Calories Foot-pounds → Kilocalories Foot-pounds → Watt-hours Foot-pounds → Kilowatt-hours Foot-pounds → Megawatt-hours Foot-pounds → BTU Foot-pounds → Electronvolts Foot-pounds → Ergs

📐 How to Use

  1. Pick the unit your quantity is in from the From dropdown, such as Kilojoule or kWh, and type the amount into the field below it.
  2. Pick the unit you want from the To dropdown; the converted energy shows in the result panel as soon as either selection or the value changes.
  3. Use the swap button between the two columns to reverse the direction, then press Copy to take the converted number.
  4. Choose a card from the Common Energy Conversions grid for a frequent pairing, or open a combination in the All Energy Conversions list for a dedicated page with a conversion table.

❓ Frequently Asked Questions

QHow many joules are in a kilocalorie?
A kilocalorie is 4,184 joules, or 4.184 kilojoules. This is the Calorie that food labels report, so a 500 Calorie meal is 2,092 kilojoules. The small calorie used in science is 4.184 joules, a thousand times less, and both units are listed separately.
QWhat is 1 kWh in joules?
One kilowatt-hour is 3,600,000 joules, which is 3.6 megajoules, because a kilowatt held for 3,600 seconds delivers that much energy. The same amount is 1,000 watt-hours, 3,412.141156 BTU, or 860.42065 kilocalories. It is the unit electricity meters bill in.
QWhat is an electronvolt?
An electronvolt is 1.60218e-19 joules, the energy one electron picks up crossing a potential of one volt. Atomic and particle physics use it because joules are unwieldy at that scale: a single joule is 6.241496e18 electronvolts. Results this extreme are shown in scientific notation.
QIs a BTU the same as a joule?
No. One BTU is 1,055.056 joules, originally the heat needed to raise a pound of water by one degree Fahrenheit. Air conditioners are rated in BTU per hour, which measures power rather than energy, so those figures belong in the power converter instead.

ℹ️ About Energy Conversion

Energy is a single quantity that a dozen fields each gave their own unit. A joule is a newton-meter, food labels count kilocalories, utility bills count kilowatt-hours, heating equipment is rated in BTU, and particle physics works in electronvolts of 1.60218e-19 joules. The calorie is the trap almost everyone meets. The Calorie printed on nutrition labels is really a kilocalorie, 4,184 joules, while the calorie of physics and chemistry is 4.184 joules, one thousandth as large. Both appear in the unit list, spelled apart as calorie and kilocalorie.

Thirteen units are supported, from electronvolts and ergs through to megawatt-hours. The joule is the base: an entry is multiplied by its unit's energy in joules, then divided by that of the unit you want. Very large and very small answers appear in scientific notation, while ordinary ones keep four to eight decimals. The calculation stays in your browser.

📏 13 Supported Units

Joule (J), Kilojoule (kJ), Megajoule (MJ), Gigajoule (GJ), Calorie (cal), Kilocalorie (kcal), Watt-hour (Wh), Kilowatt-hour (kWh), Megawatt-hour (MWh), BTU (BTU), Electronvolt (eV), Erg (erg), Foot-pound (ft·lb).

Length Temperature Area Volume Weight Time Pressure Energy Power Force Speed Angle Data Storage Numbers Volume (Dry) Fuel Economy Acceleration Density Torque Frequency Electric Current Electric Resistance Electric Potential Illumination Image Resolution