Kilojoules to Calories Converter

Kilojoules to Calories

Convert kilojoules (kJ) to calories (cal). Both measure work and power, and the conversion comes up in nutrition, electricity, fitness work.

The Formula

`` calories = kilojoules × 239.005736138 kilojoules = calories × 0.004184 `

One kilojoule is 239.0057 calories, and one calory is 0.004184 kilojoules.

Conversion Table

Kilojoules	Calories
1 kJ	239.0057 cal
2 kJ	478.0115 cal
5 kJ	1,195.03 cal
10 kJ	2,390.06 cal
25 kJ	5,975.14 cal
50 kJ	11,950.29 cal
100 kJ	23,900.57 cal
500 kJ	119,502.87 cal
1,000 kJ	239,005.74 cal

The Other Direction

Calories	Kilojoules
1 cal	0.004184 kJ
2 cal	0.008368 kJ
5 cal	0.02092 kJ
10 cal	0.04184 kJ
25 cal	0.1046 kJ
50 cal	0.2092 kJ
100 cal	0.4184 kJ
500 cal	2.092 kJ
1,000 cal	4.184 kJ

What Each Unit Is

Kilojoules (kJ) — 1,000 joules. The metric food-energy unit outside North America.

Calories (cal) — the energy to raise one gram of water by one degree Celsius, or 4.184 joules — the "small" calorie. A 19th-century thermal unit, displaced by the joule in physics but retained in nutrition.

A Sense of Scale

• An apple holds about 400 kJ
• Daily intake is around 8,700 kJ
• A gram of sugar holds about 4,000 small calories

Precision

The factor 239.005736138 is rounded. For engineering work carry more digits than the table above, and round only at the end — rounding at each step compounds.

Watch Out For

• Food labels say "calorie" but mean kilocalorie — 1,000 of these. A 200-calorie snack is 200 kcal, or 837 kJ.

In Code

`javascript const kilojouleToCalorie = (value) => value * 239.005736138; ``

Where This Conversion Comes Up

• Nutrition
• Electricity
• Fitness
• Heating
• Fuel

How Many Decimals Do You Need?

Rounding the factor costs accuracy, and how much depends on the factor. Converting 137 kJ with the factor truncated at each decimal place:

Decimals kept	Factor	137 kJ becomes	Error
0	239	32,743	0.0024%
1	239	32,743	0.0024%
2	239.01	32,744.37	0.0018%
3	239.006	32,743.82	0.0001%
4	239.0057	32,743.78	—

A rule that holds for any conversion: round once, at the end. Rounding the factor and then multiplying compounds the error through every subsequent calculation, while carrying full precision and rounding the final answer does not.

The right number of significant figures is set by your input, not by the converter. If you measured kilojoules to three significant figures, the answer in calories is only good to three — writing more digits claims precision the measurement never had.