Energy Converter

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Result418.4

Food energy and electrical energy in the same units

Convert between joules, calories, kilocalories, watt-hours, kilowatt-hours and BTU. Useful for nutrition labels and electricity bills alike.

Energy is measured in wildly different units depending on the field: food labels use kilocalories, electricity bills use kilowatt-hours, physics uses joules, heating equipment uses BTU.

They all describe the same quantity. A 2000 kcal daily diet is about 8.4 megajoules, or roughly 2.3 kWh — about what a fan heater uses in a couple of hours.

What this calculator shows

Conversion across seven energy units
Nutrition units alongside electrical and heating units
Precision suitable for both label reading and technical work

What to keep in mind

Uses the thermochemical calorie: 1 cal = 4.184 J.
A food 'Calorie' with a capital C is a kilocalorie — 1000 of the physics kind.

FAQs

Why do food labels show both kcal and kJ?

Because regulations in many countries require the SI unit alongside the familiar one. They are the same energy expressed twice: 100 kcal is 418 kJ.

Is a Calorie the same as a calorie?

No, and the capital letter is doing enormous work. A food Calorie is 1000 physics calories, so a 500 Calorie meal is 500,000 calories in strict terms.

How much is one kilowatt-hour?

3.6 million joules — running a 1000 W appliance for an hour. It is the unit your electricity meter counts.

What is a BTU used for?

Heating and air conditioning, mostly in the US and UK. One BTU raises a pound of water by one degree Fahrenheit, and it is about 1055 joules.

Worked example

A chocolate bar in electrical terms

Input: 250 kcal

Output: About 1046 kJ, or 0.29 kWh

Note: That single bar holds roughly the energy a 60 W bulb uses in five hours.

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