How many calories are in 1 joule?

1 joule equals 0.2390057361 calories, using the exact defined conversion factor rather than an estimate.

How do I convert joule to calorie?

Multiply the joule value by 0.2390057361. The converter above does this instantly to whatever precision you set.

How do I convert calorie back to joule?

Use the reverse factor: 1 calorie equals 4.184 joules. You can also use the swap control in the converter above to flip the direction instantly.

Is the joule to calorie conversion exact?

Yes. The thermochemical calorie used in this converter is defined as exactly 4.184 joules. That fixed definition is what the converter above uses, so any rounding you see is a display choice, not a limitation of the math.

Joules to Calories Converter

Q: What is a joule?

Joule (J) measures energy. The joule is the SI derived unit of energy, defined as the work done by one newton acting over one meter. It is classified as a SI derived unit.

Q: What is a calorie?

Calorie (cal) measures energy. The thermochemical calorie used in this converter is defined as exactly 4.184 joules. It is classified as a Non-SI unit (limited use with SI).

About Converting Joules to Calories

Joule and Calorie both measure a quantity used in structural or mechanical engineering — commonly stress, pressure, force, torque, power, or energy — where converting between the unit conventions used in different regions, industries, or equipment specifications is a routine part of design work. Joule is typically associated with standard scientific and engineering energy unit worldwide, while Calorie is typically associated with nutrition labeling in the US and several other countries still commonly uses the kilocalorie (as 'Calorie').

Formula

calories = joules × 0.239005736138

This factor comes from each unit's defined relationship to the category's base unit: 1 joule equals 1 base unit, and 1 calorie equals 4.184 base units, so dividing one by the other gives the direct joule-to-calorie factor of 0.239005736138.

Simple example

1 J × 0.2390057361 = 0.2390057361 cal

1 joule = 0.2390057361 calories.

Real-world example

100 J × 0.2390057361 = 23.90057361 cal

100 joules = 23.90057361 calories.

Conversion table

Joule (J)	Calorie (cal)
1 J	0.2390057361 cal
10 J	2.390057361 cal
50 J	11.95028681 cal
100 J	23.90057361 cal
500 J	119.5028681 cal
1,000 J	239.0057361 cal

Reverse conversion: Calorie to Joule

0.2390057361 cal × 4.184 = 0.9999999998 J

0.2390057361 calories = 0.9999999998 joules.

joules = calories × 4.184

For a page dedicated to this direction, see Calorie to Joule.

Joule vs. Calorie

Aspect	Joule	Calorie
Family	SI derived unit	Non-SI unit (limited use with SI)
Typical use	Physics and engineering energy calculations	Food energy labeling (as kilocalories, often written 'Calories')
Where it's used	Standard scientific and engineering energy unit worldwide	Nutrition labeling in the US and several other countries still commonly uses the kilocalorie (as 'Calorie')

Understanding the Joule

Joule (J) measures energy. The joule is the SI derived unit of energy, defined as the work done by one newton acting over one meter. It is classified as a SI derived unit.

Where it's used: Standard scientific and engineering energy unit worldwide

Uses of the Joule today

Physics and engineering energy calculations
Electrical energy in scientific contexts (though kWh is used for billing)
Nutrition labeling in some countries (alongside or instead of calories)

History of the Joule

The joule is named after English physicist James Prescott Joule, whose experiments in the 1840s established the mechanical equivalent of heat — demonstrating that mechanical work and heat are interchangeable forms of energy, foundational to the first law of thermodynamics.

The unit itself was formally adopted as the SI derived unit of energy by international agreement as part of the broader SI system, defined coherently from the base units (kg, m, s) rather than as an independent physical standard.

Historical origin. Joule was not the invention of a single named person; it developed through the process described above.

Understanding the Calorie

Calorie (cal) measures energy. The thermochemical calorie used in this converter is defined as exactly 4.184 joules. It is classified as a Non-SI unit (limited use with SI).

Where it's used: Nutrition labeling in the US and several other countries still commonly uses the kilocalorie (as 'Calorie')

Calorie vs. Calorie (kilocalorie). Food labels' capitalized 'Calorie' is actually one kilocalorie (1,000 small calories) — a long-standing labeling convention that causes frequent confusion.

Uses of the Calorie today

Food energy labeling (as kilocalories, often written 'Calories')
Historical chemistry and thermodynamics contexts

History of the Calorie

The calorie was originally defined in the early 19th century as the heat needed to raise one gram of water by one degree Celsius, but different scientific traditions defined it at slightly different reference temperatures, producing several close but non-identical 'calorie' values historically (15 °C calorie, mean calorie, thermochemical calorie).

To resolve this ambiguity, the thermochemical calorie was fixed by convention at exactly 4.184 joules; the very similar International Table calorie is fixed at exactly 4.1868 joules. The nutritional 'Calorie' seen on food labels is actually a kilocalorie (1,000 calories).

Historical origin. Calorie was not the invention of a single named person; it developed through the process described above.

Joule — sources

BIPM SI Brochure — Coherent derived units — Defines the joule as the SI unit of energy.

Calorie — sources

NIST Special Publication 811 — Documents the thermochemical calorie's exact joule equivalence.

Joules to Calories Converter — J to cal

Engineering Converter