Energy Converter
Convert energy between joules, kilowatt-hours, calories, BTU, electronvolts, and 19 other units. Enter one value and pick its unit, then either see the equivalent in every unit at once or pick a single target unit.
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Guides
The Energy Converter turns a single energy measurement into its equivalent across 24 units at once. Enter one value, choose the unit it is expressed in, and the tool instantly builds a table showing the same energy in joules, kilowatt-hours, calories, BTU, electronvolts, and more.
Energy shows up in wildly different units depending on the field: physics uses joules and electronvolts, nutrition uses calories, home energy bills use kilowatt-hours, HVAC and gas heating use BTU and therms, and the energy industry uses tonnes of oil equivalent. This tool bridges all of them at once.
How to use it
- Type the amount you want to convert into the Amount box.
- Pick the unit that amount is in from the Unit list.
- Optionally set the Decimal precision (0 to 10 places) for how the results are rounded.
The results table updates automatically. Very large or very small results (electronvolts, gigawatt-hours) are shown in scientific notation so nothing is lost to rounding. Use the copy and download buttons to grab every conversion as CSV.
How many joules are in a kilowatt-hour?
One kilowatt-hour equals exactly 3,600,000 joules (3.6 megajoules) — it's the energy of running a 1,000-watt device for one hour, which is why utility bills use it directly.
What is the difference between a calorie and a kilocalorie?
A "calorie" as used in nutrition labels is actually a kilocalorie (1,000 small calories, or "cal" in physics). This tool lists both the small calorie (4.184 J) and the kilocalorie (4,184 J) so you can tell them apart explicitly.
What is an electronvolt used for?
The electronvolt (eV) measures the tiny energies involved in atomic and particle physics — one eV is the energy gained by a single electron moving through a 1-volt potential difference. It's far too small a unit for everyday use, which is why the table also includes keV, MeV, and GeV.
How does BTU relate to therms?
A therm is defined as exactly 100,000 BTU, and is commonly used for billing natural gas in the US. One BTU is roughly the energy released by burning a single wooden matchstick.
Privacy
Every conversion runs entirely in your browser. Nothing you enter is sent to a server, logged, or stored.