How to use the energy converter
This energy converter lets you switch between common energy units in one place. Choose the unit you are converting from and the unit you want to convert to, enter a non-negative value, and click "Convert" to see the result. A "Swap" button reverses the from and to units so you can check conversions in both directions without retyping. All conversions use the Joule (J) as the base: every unit is defined relative to Joules, so the tool stays consistent and accurate.
Energy conversion is useful in many situations. In nutrition, food energy is often in kilocalories (kcal), while physics and chemistry use Joules. Electricity bills show consumption in kilowatt-hours (kWh). Heating and cooling in the US are often described in BTU. Scientists sometimes work in electronvolts (eV) for atomic-scale energy. Whether you are comparing a snack's calories to Joules, converting your monthly kWh to BTU, or doing a physics problem, having a single tool that handles J, kJ, cal, kcal, Wh, kWh, BTU, and eV saves time and reduces errors.
The converter runs entirely in your browser. There is no sign-up, no download, and no delay. It is designed to be mobile-friendly: the two-column layout stacks on small screens, inputs have a comfortable touch size, and the result appears next to your input so you can compare at a glance. Results are shown with up to six decimal places when needed. Note that on food labels, "calories" usually means kilocalories (kcal); the small calorie (cal) is 1/1000 of a kcal.
Bookmark this page for quick access whenever you need to convert energy between different units. Whether you are counting calories, reading a utility bill, or solving an equation, this free energy converter provides fast, accurate, and easy-to-read results on any device.