Convert kilocalorie (food cal) to kilojoule.

About this conversion

Calories-to-kilojoules: multiply by 4.184. The standard conversion for nutrition labels — Europe and Australia primarily use kJ; the US uses kcal (labeled "Calories" with capital C, equivalent to 1000 small calories).

Formula

kJ = kcal × 4.184

Real-world examples

Reference values

Tips & tricks

• On nutrition labels: "Calories" (capital C) means kilocalories. A "100 Calorie" snack is 100 kcal = 418 kJ.
• EU food labels are required to show both kJ (primary) and kcal (secondary).
• Rough mental conversion: multiply kcal by 4 to get approximate kJ.

Origin & history

The calorie was defined in the early 1800s as the heat needed to raise 1 gram of water 1 °C. The "food calorie" or kilocalorie is 1000 of those. The joule (SI) was named after James Prescott Joule, who established the mechanical equivalent of heat in the 1840s.

What is a kilocalorie (food calorie)?

One kilocalorie equals 1,000 small calories or about 4,184 joules. Food labels use "Calorie" (capitalized) to mean kcal. Food energy in the US — when a label says "240 Calories", it means 240 kcal.

What is a kilojoule?

One kilojoule equals exactly 1,000 joules. Food energy labels in Europe and Australia (an apple is about 200 kJ), thermal calculations.

Real-world examples of kcal

Some everyday comparisons can make the unit easier to picture.

• 1 kcal — the energy of a sip of orange juice.
• 80 kcal — a medium banana.
• 2000 kcal — an adult daily food energy guideline.

How to convert kilocalorie (food calorie) to kilojoule

To convert a value from kilocalorie (food calorie) (kcal) to kilojoule (kJ), apply the conversion factor shown in the formula above. The calculation is the same whether you do it by hand, in a spreadsheet, or with the live converter on this page.

Steps:

1. Take your input value in kcal.
2. Apply the formula see formula above.
3. The result is your value in kJ.

For repeated calculations, save the formula in a spreadsheet or use the live converter at the top of this page — it handles the math automatically and displays the result as you type.

Frequently asked questions

How do I convert kcal to kJ?

Apply the formula kcal → kJ shown above, or just type your value into the converter at the top of this page. The result updates instantly.

Which is bigger, kcal or kJ?

This depends on the conversion ratio in the formula. If the factor multiplied by your value gives a larger number, then kJ is the smaller unit (so it takes more of them to express the same quantity). If the result is smaller, then kJ is the larger unit.

When would I use kcal versus kJ?

Both units measure energy, so the choice depends on context. Kilocalorie (food calorie) is typically used for food labeling, batteries, fuel, and electric utility billing; kilojoule similarly. Most professional fields standardize on one or the other based on regional conventions or technical tradition.

How precise is this kcal to kJ conversion?

The conversion factor shown is the internationally defined exact value (or the best-published approximation if the relationship is irrational, like degrees-to-radians). The live converter on this page uses double-precision floating-point math, accurate to about 15 significant digits — far beyond any practical engineering need.

Is the conversion ratio exact, or an approximation?

Most unit conversions between SI metric units, and between SI and US customary units, have been formally defined as exact values since the 1959 international yard-pound agreement and subsequent SI redefinitions. Exceptions are unit pairs that involve irrational numbers (radians, e.g.) or empirical conversions (like food calories, which depend on temperature). When in doubt, consult the formula at the top of this page.

Related conversions

See also