How many joules are in a kilowatt-hour?

One kilowatt-hour is 3,600,000 joules, or 3.6 megajoules. The kilowatt-hour is the unit your power bill charges in.

What is the difference between a calorie and a kilocalorie?

A food Calorie is actually a kilocalorie, 1000 small calories, which is about 4184 joules. So a 2000 Calorie diet means 2000 kilocalories.

A British thermal unit is about 1055 joules. It is common in heating and cooling, where appliance outputs are sometimes quoted in BTU.

Energy Converter

This energy converter moves a figure between the units used to measure energy, the capacity to do work or produce heat. Energy crops up in many units depending on the context: science uses joules and kilojoules, food labels use calories and kilojoules, electricity is billed in kilowatt-hours, and heating sometimes uses BTU, so converting between them is a common need. You enter a value, pick the unit it is in and the unit you want, and the converter gives the result instantly. The conversions use the standard definitions, where a kilojoule is 1000 joules, a food Calorie is a kilocalorie of about 4184 joules, a watt-hour is 3600 joules, a kilowatt-hour is 3.6 million joules, and a BTU is about 1055 joules. This is useful across everyday life and study: comparing the energy on a food label shown in both kilojoules and Calories, understanding the kilowatt-hours on your power bill, or sizing heating quoted in BTU against an appliance rated in kilowatts. New Zealand food labels lead with kilojoules, so converting to the more familiar Calories can make a nutrition panel easier to read. Enter a value and choose your units to see the converted energy straight away, with the result shown to a sensible precision.

How it works

Each unit has a known size in joules, the SI base unit of energy. The converter turns your value into joules, then into the target unit, so any two units convert in one step.

Worked example

A 2000 Calorie diet is 2000 kilocalories, and at about 4184 joules each that is roughly 8,368,000 joules, or 8368 kilojoules, the figure you would see on a New Zealand food label.

Related calculators

Power Converter: watts and horsepower.
Kinetic Energy Calculator: energy of motion.
Specific Heat Calculator: heat energy.
Calorie Calculator: daily energy.

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