What is the Energy Conversion Calculator?
This tool converts a quantity of energy from one unit to another. Energy can be expressed in many units — joules, calories, kilowatt-hours, BTU, electronvolts and more — depending on whether you are dealing with food, electricity, mechanics or physics. Because all of these describe the same physical quantity, any value can be translated into any other unit using a simple two-step factor method anchored to the SI base unit, the joule.
How to use it
Enter the energy value, pick the unit you are converting from, then pick the unit you want to convert to. The calculator first turns your input into joules, then into the target unit. The result and the intermediate joule value are both shown.
The formula explained
Every unit has a factor equal to how many joules one of that unit contains. For example \(1\ \text{kcal} = 4184\ \text{J}\) and \(1\ \text{kWh} = 3{,}600{,}000\ \text{J}\). The conversion is:
$$\text{value}_{target} = \dfrac{\text{value}_{source} \times f_{source}}{f_{target}}$$By routing through joules, a single set of factors handles every possible pairing of units.
Worked example
Convert 1000 calories to joules. The factor for calories is 4.184 J/cal and joules is 1. So energy in joules \( = 1000 \times 4.184 = 4184\ \text{J}\), and the target (joules) value:
$$v_{target} = E_J / f_{target} = 4184 / 1 = 4184\ \text{J}$$FAQ
Is a calorie the same as a food Calorie? No — a food "Calorie" (capital C) is a kilocalorie (\(1000\ \text{cal} = 4184\ \text{J}\)). Use the kcal option for nutrition labels.
Which calorie definition is used? The thermochemical calorie of exactly \(4.184\ \text{J}\).
How many joules are in a kilowatt-hour? Exactly \(3{,}600{,}000\ \text{J}\), since \(1\ \text{kW} \times 1\ \text{h} = 1000\ \text{W} \times 3600\ \text{s}\).
