Energy Conversions
Convert energy units — joules, calories, kWh, BTU. Free calculators for nutrition labels, electricity bills, and physics.
7 units · 5 conversions
Energy quantifies the capacity to do work or produce heat. Food labels use kilocalories (often labeled "Calories"); electricity bills use kilowatt-hours; HVAC and fuel discussions use BTU.
These units measure the same physical quantity but at different scales. One food Calorie (kilocalorie) equals 4,184 joules. One kWh equals 3.6 million joules. Our converters bridge nutrition, utility, and science contexts.
Popular energy conversions
Real-world example
A snack label shows 250 Calories (kcal) and you want the value in kilojoules as used on some international labels. Converting gives about 1,046 kJ.
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Energy units explained
- Joules (J) · base unit
- Also: joules
- Kilojoules (kJ)
- Also: kilojoules
- Calories (cal)
- Also: calories
- Kilocalories (kcal)
- Also: kilocalories, food calories
- Watt Hours (Wh)
- Also: watt hours
- Kilowatt Hours (kWh)
- Also: kilowatt hours
- British Thermal Units (BTU)
- Also: british thermal units, btu
Frequently asked questions
- Is a food Calorie the same as a calorie?
- On nutrition labels, "Calorie" with a capital C means kilocalorie (1,000 small calories). One kcal = 4,184 J.
- How many joules are in a kWh?
- One kilowatt-hour equals exactly 3,600,000 joules (3.6 MJ).