Joules to Calories (J to cal) Converter

1 joule equals 0.23900574 calories — multiply the number of joules by 0.23900574, or divide by 4.184, to convert. This uses the thermochemical calorie, defined as exactly 4.184 joules.

The formula

To convert joules to calories, multiply by the factor:

calories = joules × 0.23900574

For example, 100 J × 0.23900574 = 23.900574 cal. To reverse it, multiply calories by 4.184 to get joules.

Conversion table

Worked example

Suppose a reaction releases 800 joules and you want calories. Multiply: 800 × 0.23900574 = 191.2 cal. Reversing, 191.2 × 4.184 ≈ 800 joules. A 2,000-joule measurement is 2,000 × 0.23900574 ≈ 478 cal. Remember these are small (thermochemical) calories; to reach one food Calorie you would need 4,184 joules, or 1,000 of these small calories, which is why nutrition labels use kilocalories instead. Doubling the joules doubles the calories, so 1,600 joules is about 382.4 cal. The converter applies the 4.184 definition automatically, so your physics and chemistry energy figures stay consistent whether you work forward or backward. This is especially useful when lab instruments report joules but a problem set asks for calories, and the reverse is a single division by 0.23900574.

How to convert online

Let the tool apply the exact factor for you:

1. Type the number of joules into the first box.
2. Read the equivalent in calories instantly in the second box.
3. Enter a calorie value to convert back to joules.

Use the Joule to Calorie Converter — free and instant in your browser.

Where this conversion is used

Joules-to-calories conversions appear in physics and chemistry problems, thermodynamics, and nutrition science, where energy is measured in joules on lab equipment but reported in calories. Note that food labels use kilocalories (Cal), which are 1,000 of these small calories.

FAQ

How many calories are in a joule?

One joule equals 0.23900574 calories. One hundred joules equal about 23.9 calories.

What is the formula to convert joules to calories?

Multiply the joule value by 0.23900574: cal = J × 0.23900574.

How do I convert calories back to joules?

Multiply the calorie value by 4.184. For example, 1 calorie = 4.184 joules.

Is the conversion exact?

Yes for the thermochemical calorie, which is defined as exactly 4.184 J; 0.23900574 is the rounded reciprocal of that value.

Related converters

• Calorie to Joule Converter
• Joule to Kilocalorie Converter
• Joule to Kilojoule Converter
• Joule to Watt-hour Converter

Built by ByteVancer

ByteTools is a free product of ByteVancer, a software and web development studio. Need custom calculators, scientific tools or web apps built to the same fast, private standard? ByteVancer can help.