Energy Converter
A food label in kcal, a battery in watt-hours, physics homework in joules — set the unit and watch every equivalent fall into line.
How it works
The joule is the base unit for all of it. Your entry becomes joules, then converts out to kilojoules, calories, kilocalories, watt-hours, and kWh. One number drives the entire grid, live.
The calorie confusion is worth clearing up. The 'calorie' on a food label is really a kilocalorie — 4,184 joules — while a plain calorie is a thousand times smaller. That's why a candy bar reads 250 rather than 250,000.
Electricity uses watt-hours. A kilowatt-hour is 3.6 million joules, and it's what your power bill charges for. So a 2,000 W heater running an hour uses 2 kWh, or 7.2 million joules of energy.
Frequently asked questions
How many joules are in a calorie?
A single calorie is 4.184 joules. But a food 'Calorie' is actually a kilocalorie, which is 4,184 joules — a factor of a thousand that trips up almost everyone reading nutrition labels.
How many joules in a kWh?
One kilowatt-hour equals 3,600,000 joules. It comes from 1,000 watts sustained for 3,600 seconds, and it's the unit utilities bill you by.
Are food calories the same as kilocalories?
They are. The capital-C Calorie on packaging is a kilocalorie, equal to 1,000 small calories. A 500-Calorie meal is 500 kcal, or roughly 2.1 million joules.