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Kilocalories to Joules Converter

Convert kilocalories to joules — 1 kcal = 4,184 J. Food energy reference, calorie vs kilocalorie guide, and conversion table.

kcal

Joules

2,092,000

J

500 kcal = 2,092,000 J

J = kcal × 4184

How to Convert Kilocalories to Joules

Multiply the kilocalorie value by 4,184 to get joules. The kilocalorie is the familiar food "Calorie" used on nutrition labels, while the joule is the SI unit of energy.

Conversion Formula

  • kcal to Joules: J = kcal × 4,184
  • Joules to kcal: kcal = J ÷ 4,184

Common Conversions

KilocaloriesJoules
0.52,092
14,184
520,920
1041,840
25104,600
50209,200
100418,400
150627,600
2501,046,000
5002,092,000
7503,138,000
1,0004,184,000
1,5006,276,000
2,0008,368,000

Understanding the Units

What Is a Kilocalorie?

A kilocalorie (kcal) is the amount of energy needed to raise the temperature of one kilogram of water by one degree Celsius at standard atmospheric pressure. It equals 1,000 thermochemical calories. In everyday language — especially on US food labels — it is written as "Calorie" with a capital C. When a nutrition label says a banana has 105 Calories, it means 105 kilocalories.

What Is a Joule?

The joule (J) is the SI unit of energy, named after English physicist James Prescott Joule. One joule equals the work done when a force of one newton moves an object one meter (1 J = 1 N·m). It also equals one watt-second of electrical energy. The joule connects neatly to other SI units — power in watts, force in newtons, and voltage in volts — which is why the international scientific community adopted it as the standard energy unit.

Calorie vs Kilocalorie

The naming causes widespread confusion. There are two "calories":

  • Small calorie (cal): the energy to heat 1 gram of water by 1°C. Equals 4.184 joules.
  • Large Calorie or kilocalorie (Cal / kcal): the energy to heat 1 kilogram of water by 1°C. Equals 4,184 joules — exactly 1,000 small calories.

US food labels use "Calories" (capital C) to mean kilocalories. EU labels use kilojoules (kJ) as the primary unit, with kcal shown alongside. To convert between the two label formats: 1 kcal = 4.184 kJ.

Common Foods in Kilocalories and Joules

FoodkcalJoules (kJ)
Boiled egg78326 kJ
Medium apple95397 kJ
Banana105439 kJ
Chicken breast (100 g)165690 kJ
Slice of pizza2851,192 kJ
Big Mac5632,354 kJ

Related converters: joules to kilocalories, kilocalories to kilojoules, kilocalories to calories, calories to joules, and joules to kilowatt-hours.

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FAQ

How many joules are in one kilocalorie?

One kilocalorie equals exactly 4,184 joules. This is based on the thermochemical definition where 1 calorie = 4.184 joules.

How do I convert kcal to joules?

Multiply the kcal value by 4,184. For example, 3.5 kcal × 4,184 = 14,644 J.

How much energy is in a typical meal in joules?

A 600 kcal meal contains about 2,510,400 joules (2.51 MJ). The daily recommended 2,000 kcal intake equals 8,368,000 joules (8.37 MJ).

Why are both kcal and joules used in science?

Joules are the SI standard, but kilocalories remain common in nutrition, biochemistry, and older scientific literature. Many food databases still report energy in kcal alongside kJ.

What is the difference between a calorie and a kilocalorie?

A kilocalorie (kcal) equals 1,000 calories. The "Calories" on US food labels are actually kilocalories. A small "c" calorie (cal) is 4.184 joules; a large "C" Calorie (Cal) or kilocalorie is 4,184 joules.

How do European and American food labels differ?

US labels list energy in "Calories" (which are kilocalories). EU labels display energy in kilojoules (kJ) as the primary unit, often with kcal alongside. To convert the EU value: divide kJ by 4.184 to get kcal.

How many joules does daily exercise burn?

A 30-minute jog burns roughly 300 kcal (1,255,200 J or 1.26 MJ). An hour of cycling burns about 500 kcal (2,092,000 J or 2.09 MJ). These values vary with body weight and intensity.

Why did SI adopt joules over calories?

The joule fits consistently into the SI framework — it connects directly to watts (1 W = 1 J/s), newtons (1 J = 1 N·m), and other SI units. The calorie, defined by the specific heat of water, introduced temperature-dependent variability that made it less suitable as a universal standard.