Energy Unit Converter

The Energy Unit Converter is a free online tool that convert between joules, kilocalories, kilowatt-hours, btu, electron-volts, therms, and more energy units. It runs entirely in your browser with no installation or sign-up needed.

1 kcal = 1000 cal = 4184 J. Food label "Calories" are actually Kilocalories.

Eleven: J, kJ, MJ, cal, kcal, Wh, kWh, BTU, ft·lbf, eV, therm.

Yes — client-side, no registration.

Absolutely. The Energy Unit Converter processes everything client-side in your browser. No data is uploaded to or stored on any server. Your content remains private on your device at all times.

Yes, the Energy Unit Converter is fully responsive and works on smartphones and tablets. You can use it on any device with a modern web browser -- no app download required.

No account or registration is needed. Simply open the Energy Unit Converter in your browser and start using it immediately. There are no sign-up walls or usage restrictions.

Simply enter your input in the provided field, adjust any settings to your preference, and the tool will process it instantly. You can then copy the result to your clipboard or download it.

The Energy Unit Converter works in all modern browsers including Chrome, Firefox, Safari, Edge, and Opera. For the best experience, use the latest version of your preferred browser.

One kilowatt-hour equals about 3,412.14 BTU. The relationship comes from defining both units against the Joule: 1 kWh is exactly 3,600,000 J, and 1 BTU is roughly 1,055.06 J, so dividing 3,600,000 by 1,055.06 gives 3,412.14. This conversion matters when you compare an electric heater rated in kilowatts against a gas furnace or air conditioner rated in BTU, since the two industries label the same energy differently. Going the other way, 1 BTU is about 0.000293 kWh, and 10,000 BTU is roughly 2.93 kWh. Rounding the factor to 3,412 is fine for everyday estimates, but use more decimals for engineering work. Enter your kWh or BTU value above and the converter shows the exact equivalent plus the underlying 1-to-1 ratio, so you can check the math instead of memorizing it.

A food "Calorie" with a capital C is actually a kilocalorie, where 1 kcal equals 4,184 joules. To reach kilowatt-hours, convert to joules first, then divide by 3,600,000, since 1 kWh is 3.6 million joules. That makes 1 kcal about 0.00116 kWh. A 2,000-Calorie daily diet therefore holds roughly 2.32 kWh of chemical energy, enough to run a 100-watt bulb for about a day, which is a striking way to picture how much energy a meal carries. Keep in mind this is the food's stored energy, not how efficiently your body uses it. The converter handles this in one step: pick kilocalorie as the "from" unit and kilowatt-hour as the "to" unit, and it prints both the result and the exact conversion factor it used.

A BTU and a Therm both measure heat energy, but they differ in scale by a factor of 100,000. A BTU, the British Thermal Unit, is the energy needed to raise one pound of water by one degree Fahrenheit, about 1,055 joules. A Therm is simply defined as 100,000 BTU, which works out to roughly 105.5 megajoules. You usually meet the BTU on appliance specifications such as furnaces, stoves, and air conditioners, while the Therm appears on natural-gas bills as the billing unit for the gas you burn. Because the Therm is so much larger, household gas usage that would be millions of BTU is conveniently expressed as a handful of Therms. The converter includes both units, so you can turn a Therm reading on your gas statement into BTU, joules, or kWh and compare it directly against an appliance rating.

An electron-volt is tiny because it describes the energy of a single charged particle, not a macroscopic quantity. By definition, 1 eV is the energy gained by one electron moving across a potential difference of one volt, which equals about 1.602 x 10 to the power of minus 19 joules. That is a fraction of a joule with eighteen zeros after the decimal point, so even a visible-light photon carries only a couple of eV. The unit exists precisely because joules are absurdly large for atomic and particle physics, where using whole numbers like 13.6 eV (the energy to ionize hydrogen) is far more practical. When you convert eV in this tool, results in joules are so small that they automatically switch to scientific notation to stay readable. Enter an eV value above to see its joule equivalent without counting zeros yourself.

One kilowatt-hour equals exactly 3,600,000 joules, or 3.6 megajoules. The figure comes from multiplying power by time: a kilowatt is 1,000 joules per second, and an hour is 3,600 seconds, so 1,000 times 3,600 gives 3.6 million joules. Utilities bill in kilowatt-hours rather than joules because the joule is far too small for household use; running a typical home for a month involves hundreds of billions of joules, an unwieldy number, whereas the same usage is just a few hundred kWh. The kWh also maps cleanly onto appliance ratings, since a 2,000-watt heater running one hour consumes exactly 2 kWh. To check your own consumption, enter a kWh figure above and convert it to joules, BTU, or even kilocalories to compare energy across very different systems.