UnitConvConvert
Energy

Convert calories to kilojoules

1 cal=0.004184kJ

Use the converter below to change any calories value into kilojoules instantly — with formula, conversion table, and real-world examples.

0.004184

Conversion formula

Forward
kilojoules = calories × 0.004184
Reverse
calories = kilojoules × 239.006

Example: 10 cal × 0.004184 = 0.04184 kJ.

About both units

From

Calorie

cal

The gram calorie (small calorie) equals 4.184 joules — the energy to raise 1 g of water by 1 °C. It is a scientific unit, distinct from the nutrition "Calorie" (kcal). Largely replaced by joules in modern science.

Real-world: Raising 1 g of water 1 °C: 1 cal. A 100 kcal snack = 100,000 small calories.
Read full calorie reference →
To

Kilojoule

kJ

The kilojoule equals 1000 joules. Used on European nutrition labels (required by EU law alongside kcal), for mechanical work specifications, and some engineering contexts. A 100 g chocolate bar contains about 2100 kJ.

Real-world: 100 g chocolate: ~2100 kJ. EU daily intake (adult): ~8400 kJ. Tesla Model 3 battery: ~270 MJ = 270,000 kJ.
Read full kilojoule reference →

Calorie to Kilojoule conversion table

Common calories to kilojoules values for quick reference.

Calorie (cal)Kilojoule (kJ)
1 cal0.004184 kJ
10 cal0.04184 kJ
100 cal0.4184 kJ
500 cal2.092 kJ
1,000 cal4.184 kJ
5,000 cal20.92 kJ
10,000 cal41.84 kJ
50,000 cal209.2 kJ
100,000 cal418.4 kJ
500,000 cal2,092 kJ

Tips & common mistakes

Quick tips

  • 1 cal = 4.184 J. 1 kcal = 4184 J.
  • Scientific "calorie" and nutrition "Calorie" differ by 1000×.
  • Prefer joules in modern scientific writing.

Avoid these

  • Assuming "calories" on food labels means gram calories — they are kcal.
  • Mixing gram calories and kilocalories in calculations.
  • Confusing calorie (energy) with calorimeter (apparatus).

Frequently asked questions

How many kilojoules in a calorie?
One calorie equals 0.004184 kilojoules.
How do I convert calories to kilojoules?
Multiply the calorie value by 0.004184 to get the equivalent in kilojoules.
What is 100 calories in kilojoules?
100 calories equals 0.4184 kilojoules.
Is a calorie bigger than a kilojoule?
No. 1 calorie equals 0.004184 kilojoules, so one calorie is smaller.
How to convert calories to kilojoules without a calculator?
Multiply by 0 for a quick estimate; use a calculator for precise results.

Related energy conversions

📊 See full comparison matrix →

More from Calorie

cal → J
1 = 4.184 J
cal → MJ
1 = 4.1840e-6 MJ
cal → kWh
1 = 1.1622e-6 kWh
cal → Wh
1 = 0.001162 Wh
cal → kcal
1 = 0.001 kcal
cal → BTU
1 = 0.003966 BTU
cal → eV
1 = 2.6114e19 eV
cal → thm
1 = 3.9657e-8 thm

More to Kilojoule

J → kJ
1 = 0.001 kJ
MJ → kJ
1 = 1,000 kJ
kWh → kJ
1 = 3,600 kJ
Wh → kJ
1 = 3.6 kJ
kcal → kJ
1 = 4.184 kJ
BTU → kJ
1 = 1.05506 kJ
eV → kJ
1 = 1.6022e-22 kJ
thm → kJ
1 = 105,505.59 kJ

Conversions in other categories

WeightKilogram → PoundLengthKilometer → MileTemperatureCelsius → FahrenheitVolumeLiter → US GallonAreaSquare Meter → Square FootSpeedKilometer per Hour → Mile per HourPressureBar → Pound per Square InchPowerKilowatt → Mechanical Horsepower