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Kilocalories to Kilojoules Converter

1 kcal = 4.184 kJ (kilocalorie → kilojoule)

1 kcal = 4.184 kJ

1 kilocalorie equals 4.184 kilojoules. To convert kilocalories to kilojoules, multiply the kilocalorie value by 4.184. For quick reference: 1 kcal = 4.184 kJ, 5 kcal = 20.92 kJ, 10 kcal = 41.84 kJ, 100 kcal = 418.4 kJ.

When to use kilocalories → kilojoules

Kilocalories to kilojoules multiplies by 4.184. A 500 kcal pizza slice is 2092 kJ. Use kJ for any physics or engineering work — calorimetry, heating-water calculations, thermodynamic problem sets — and reserve kcal for nutrition labels. Mixing the two in a single energy-balance calculation is one of the most common errors in introductory thermodynamics homework.

Food manufacturers preparing EU-compliant nutrition panels must print both kJ and kcal values, and many source recipes originally formulated with US kcal figures need the kJ column calculated and rounded to regulatory conventions. A recipe rated at 320 kcal per serving requires a printed 1,339 kJ, following EU labelling rules that specify rounding to the nearest whole kilojoule. Getting this wrong on packaging is a compliance issue, not just a rounding nuisance, since regulators in several EU states actively audit printed kJ figures against the declared kcal value.

How to convert kilocalories to kilojoules

  1. Take your value

    Start with your value in kilocalories.

  2. Multiply by 4.184

    Multiply the kilocalorie value by 4.184. This is the exact conversion factor from kilocalories to kilojoules.

  3. Read the result

    The product is your value in kilojoules. For example, 5 kcal × 4.184 = 20.92 kJ.

Conversion formula

The exact factor from kilocalories to kilojoules is 4.184.

Kilojoules = Kilocalories × 4.184

Kilocalories to Kilojoules conversion table

Fifty common reference values, hand-picked for skim utility. Use the calculator above for any value not listed.

Conversion table from kilocalories to kilojoules
Kilocalories (kcal)Kilojoules (kJ)
0.001 kcal0.004184 kJ
0.01 kcal0.04184 kJ
0.1 kcal0.4184 kJ
0.5 kcal2.092 kJ
1 kcal4.184 kJ
1.5 kcal6.276 kJ
2 kcal8.368 kJ
5 kcal20.92 kJ
10 kcal41.84 kJ
20 kcal83.68 kJ
50 kcal209.2 kJ
100 kcal418.4 kJ
200 kcal836.8 kJ
250 kcal1046 kJ
500 kcal2092 kJ
1000 kcal4184 kJ
2000 kcal8368 kJ
2500 kcal10460 kJ
3600 kcal15062 kJ
5000 kcal20920 kJ
7500 kcal31380 kJ
10000 kcal41840 kJ
25000 kcal104600 kJ
50000 kcal209200 kJ
100000 kcal418400 kJ
250000 kcal1046000 kJ
500000 kcal2092000 kJ
1000000 kcal4184000 kJ
2000000 kcal8368000 kJ
3600000 kcal15062400 kJ
5000000 kcal20920000 kJ
10000000 kcal41840000 kJ
25000000 kcal104600000 kJ
50000000 kcal209200000 kJ
100000000 kcal418400000 kJ
250000000 kcal1046000000 kJ
500000000 kcal2092000000 kJ
1000000000 kcal4184000000 kJ
2000000000 kcal8368000000 kJ
5000000000 kcal20920000000 kJ
10000000000 kcal41840000000 kJ
20000000000 kcal83680000000 kJ
50000000000 kcal209200000000 kJ
100000000000 kcal418400000000 kJ
1000000000000 kcal4184000000000 kJ
10000000000000 kcal41840000000000 kJ
100000000000000 kcal418400000000000 kJ
1000000000000000 kcal4.1840 × 10^15 kJ
10000000000000000 kcal4.1840 × 10^16 kJ
100000000000000000 kcal4.1840 × 10^17 kJ

Real-world reference

A medium apple has about 95 kcal. An adult's daily energy need is roughly 2,000–2,500 kcal. In kilojoules, that gives you: 1 kcal = 4.184 kJ, 10 kcal = 41.84 kJ, 100 kcal = 418.4 kJ.

Frequently asked questions

How many kilojoules are in 1 kilocalorie?
1 kilocalorie equals 4.184 kilojoules.
How do I convert kilocalories to kilojoules?
Multiply the kilocalorie value by 4.184. So x kcal × 4.184 = the equivalent in kJ.
What is 5 kilocalories in kilojoules?
5 kilocalories equals 20.92 kilojoules.
What is 10 kilocalories in kilojoules?
10 kilocalories equals 41.84 kilojoules.
What is 100 kilocalories in kilojoules?
100 kilocalories equals 418.4 kilojoules.
How do I convert back from kilojoules to kilocalories?
Multiply the kilojoule value by 0.239006. For example, 1 kJ = 0.239006 kcal.
Is the kilocalorie bigger than the kilojoule?
Yes. 1 kilocalorie is larger than 1 kilojoule — specifically 4.184 times larger.
Are these conversion factors exact?
The factor is derived directly from the SI definitions of kilocalorie and kilojoule; the displayed value is rounded for readability, and the browser computes using IEEE 754 double-precision arithmetic.

About the kilocalorie and the kilojoule

The kilocalorie

The kilocalorie (kcal) equals exactly 4,184 joules — 1,000 small calories. This is the 'Calorie' (capital C) printed on US nutrition labels: when a food package says '250 Calories', it means 250 kcal. Outside the US, food energy is usually labeled in kJ as well.

The kilojoule

The kilojoule (kJ) equals exactly 1,000 joules. It is the standard unit on EU and many non-US nutrition labels — 1 dietary calorie ≈ 4.184 kJ. It also appears in industrial-process specifications and energy-storage ratings.

Guides that use this converter

Daily Calorie Needs IN Kilojoules
EU Food Labels KJ vs Kcal Explained
HOW Many KJ IN a Kcal

Sources