Convert energy instantly — type a value, pick your units, and every other common unit updates live below. 100% free, runs entirely in your browser, no sign-up.
Every unit below updates live from the value you enter in the "From" field above.
The "Calorie" on a nutrition label is actually a kilocalorie (1,000 small calories) — a quirk of food-labeling history that trips people up constantly, so this converter labels it explicitly as Kilocalorie. Kilowatt-hours show up on electricity bills, joules and kilojoules dominate in physics and (outside the US) on nutrition labels, and BTU is still standard for rating air conditioners and furnaces in the US.
Yes. It's completely free with no sign-up, and every conversion runs locally in your browser via JavaScript — the numbers you type are never sent to our servers.
Each unit uses its standard, internationally defined conversion factor, calculated in full precision and only rounded for display. Results are accurate to at least 6 significant figures.
This page intentionally covers the most commonly used energy units rather than an exhaustive engineering list. Use the suggestion button in the bottom-right corner of any page to request a unit and we'll consider adding it.
Tell us what to improve or which tool to add next.
