Joules to Calories Converter

Convert energy between Joules, kilojoules, calories (thermochemical) and kilocalories (food Calories) — all units shown at once.

Note: 1 food Calorie (Cal) = 1 kilocalorie (kcal) = 1000 calories (cal). The capital-C Calorie on food labels is actually a kilocalorie.

What Does This Tool Do?

Convert energy values between Joules, kilojoules, calories (thermochemical), kilocalories (food Calories) and watt-hours. All five units shown simultaneously. Clarifies the confusing cal vs kcal distinction.

Key Features

⚡
5 Units
J, kJ, cal, kcal and Wh all shown at once.
🔄
Any Direction
Convert from any unit to all others.
📋
Click to Copy
Click any card to copy the value.
📚
Clarification
Explains food Calorie vs thermochemical calorie.

How to Use

  1. Enter the energy value.
  2. Select the unit you are converting from.
  3. All other units update instantly.

Frequently Asked Questions

What is the difference between a calorie and a Calorie?▾
A calorie (lowercase) is the thermochemical calorie: 1 cal = 4.184 J. A Calorie (uppercase) on food labels is actually 1 kcal = 1000 cal = 4184 J. This is a common source of confusion.
How many joules are in a kilojoule?▾
1 kJ = 1000 J exactly.
What is a watt-hour?▾
1 Wh = 3600 J. Used for electrical energy (e.g. battery capacity, electricity bills in kWh).