Energy Converter

Convert between joules, calories, kilowatt-hours, BTU and electronvolts.

What the Energy Converter does

Energy takes many units because different fields measure it differently. Food labels use kilocalories (confusingly written as "Calories"), electricity bills use kilowatt-hours, and heating systems often use BTU or therms.

Formula

Convert to joule, then divide by the target unit's factor
Result = Value × (from factor ÷ to factor)

Inputs explained

Input	Unit	Required	Notes
Value	number	Yes	—
From	one of 11 options	Yes	—
To	one of 11 options	Yes	—

How to use it

Choose From and To.
Enter Value.
Select Calculate.

Worked example

Convert 1 kilowatt-hour to megajoules.

Value: 1
From: Kilowatt-hour
To: Megajoule

1 kWh = 3.6 MJ.

Reading the result

A food Calorie written with a capital C is a kilocalorie: a thousand small calories, or about 4,184 joules.
A kilowatt-hour is 3.6 million joules, roughly what a 2 kW kettle draws in half an hour.

Common mistakes

Reading a nutrition label’s Calories as calories. The factor of a thousand turns a 500 Calorie meal into half a million calories.
Confusing kW with kWh on an electricity bill. The first is how fast energy is used, the second is how much was used.

Frequently asked questions

Is a food Calorie the same as a calorie?

No. A food Calorie (capital C) is a kilocalorie — 1,000 small calories. A 2,000 Calorie diet is 2,000 kcal or 8,368 kJ.

How much energy is a kWh?

3.6 million joules — enough to run a 1,000 W appliance for one hour.