Energy and Calorie Converter
Convert between joules (J), calories (cal), kilocalories (kcal), watt-hours (Wh), and BTU, with food and electricity references
Convert energy between joules (J), the calories and kilocalories used in nutrition, watt-hours (Wh) for electricity, and BTU for heating and cooling — all in real time. Reference guides for food calories, phone battery capacity, and other everyday amounts help you picture what the numbers mean.
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How to use
- Enter a value in any one of the energy unit fields.
- Joules (J), calories (cal), kilocalories (kcal), watt-hours (Wh), and BTU all convert automatically.
- Use the reference table to get a feel for the scale — how a phone charge or a meal's calories compare.
FAQ
- What's the difference between a calorie (cal) and a kilocalorie (kcal)?
- One kcal equals 1,000 cal. The "Calories" listed on nutrition labels and diet plans are actually kilocalories — a 500-Calorie meal contains 500 kcal, or 500,000 small calories.
- How do watt-hours (Wh) relate to joules (J)?
- One watt is a rate of one joule per second. So running at 1 watt for one hour (3,600 seconds) delivers exactly 3,600 J — meaning 1 Wh = 3,600 J.
- Why is BTU so often used to describe air conditioner or heater capacity?
- BTU (British Thermal Unit) measures the heat needed to raise one pound of water by one degree Fahrenheit, and it became the long-standing international standard for describing how much heat an HVAC unit can move per hour — its cooling or heating capacity. That history is why it's still the go-to unit on air conditioner and heater spec sheets today, even in countries that otherwise use the metric system.