⚡ Energy Converter
Free online energy converter. Convert between joules, kilojoules, calories, kilocalories, watt-hours, kilowatt-hours and BTU.
Conversion Reference Table
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Energy Conversion Guide
Energy is measured in many different units depending on the field. In physics, the standard unit is the joule (J). In nutrition, energy is measured in kilocalories (kcal) — what we commonly call "Calories" on food labels (note the capital C). In electricity, we use kilowatt-hours (kWh). In the US, heating and cooling systems often use BTU (British Thermal Units).
One food calorie (kilocalorie) equals 4,184 joules or 4.184 kilojoules. One kilowatt-hour equals 3,600,000 joules or 3,600 kilojoules. One BTU equals 1,055.06 joules. These conversions are important in nutrition, engineering, physics and energy efficiency calculations.
Calories in Food vs. Scientific Calories
This is a common source of confusion: the "calorie" in food science is actually a kilocalorie in physics. When a food label says "200 Calories", it means 200 kcal or 200,000 scientific calories. Our converter uses kilocalories (kcal) as the food-science calorie unit, so you can easily convert between food energy and other energy units.