Convert Calories to Kilojoules
1 calorie (cal) equals 0.004184 kilojoules (kJ).
1 cal = 0.004184 kJ
Type in either box. Scientific notation works: 1.5e-3.
Converting a list? Use the bulk calorie to kilojoule converter to paste a column from Excel.
How to Convert Calorie to Kilojoule
- 1 cal = 0.004184 kJ
- 1 kJ = 239.0057361 cal
- Example: convert 15 cal to kJ: 15 cal = 15 × 0.004184 kJ = 0.06276 kJ
Reference conditions. cal: Thermochemical calorie, 4.184 J exactly. The International Table calorie is 4.1868 J.
Formula
kJ = cal × 0.004184
or kJ = cal ÷ 239.0057361377
Derivation from SI units:
- 1 cal (thermochemical) = 4.184 J (exact)
- 1 kJ = 10³ J
- 1 cal = 4.184 J ÷ 1000 J per kJ = 0.004184 kJ
Both units are defined exactly, so the factor is exact. Calorie definition: calorie; Kilojoule definition: kilojoule.
Worked examples
- A reading of 100 cal converts to 0.4184 kJ.
100 cal × 0.004184 = 0.4184 kJ - A value of 1000 cal is 4.184 kJ.
1000 cal × 0.004184 = 4.184 kJ
Calorie to Kilojoule conversion table
| Calories (cal) | Kilojoules (kJ) |
|---|---|
| 1 cal | 0.004184 kJ |
| 10 cal | 0.04184 kJ |
| 100 cal | 0.4184 kJ |
| 250 cal | 1.046 kJ |
| 500 cal | 2.092 kJ |
| 1000 cal | 4.184 kJ |
| 4184 cal | 17.505856 kJ |
| 10000 cal | 41.84 kJ |
Where it's used
Calories are used for chemistry and calorimetry, while kilojoules appear in nutrition labels (kJ per serving). Both measure energy, work and heat, so the conversion is a fixed factor.
Calorie to other energy units
| Conversion | 1 cal equals |
|---|---|
| calorie to joule | 4.184 J |
| calorie to kilojoule | 0.004184 kJ |
| calorie to megajoule | 0.000004184 MJ |
| calorie to kilocalorie | 0.001 kcal |
| calorie to watt-hour | 0.001162222222 Wh |
| calorie to kilowatt-hour | 0.000001162222222 kWh |
| calorie to BTU | 0.003965666831 BTU |
| calorie to therm | 3.966613703 × 10⁻⁸ thm |
| calorie to electronvolt | 2.611447397 × 10¹⁹ eV |
| calorie to foot-pound | 3.085960033 ft·lbf |
| calorie to erg | 41840000 erg |
Frequently asked questions
How many kilojoules are in 1 calorie?
1 cal = 0.004184 kJ.
How do I convert calories to kilojoules?
Multiply the value in cal by 0.004184, or divide it by 239.0057361. For example, 15 cal × 0.004184 = 0.06276 kJ.
Is the cal to kJ conversion exact?
Yes. Both units are defined exactly, and 1 cal is exactly 0.004184 kJ.
Sources
- Guide for the Use of the International System of Units (SI), NIST Special Publication 811, 2008 Edition, National Institute of Standards and Technology , Appendix B.8, "calorie (thermochemical) (cal_th)".
- The International System of Units (SI), 9th edition (SI Brochure), Bureau International des Poids et Mesures , Table 7, SI prefixes.
Last reviewed: . Factors are stored exactly and computed with 50-digit decimal arithmetic. See how we verify conversion factors.
Cite this page
APA
Scientific Converters. (2026, October 15). Convert Calories to Kilojoules. Retrieved October 17, 2026, from https://scientificconverters.com/energy/calories-to-kilojoules/
IEEE
Scientific Converters, "Convert Calories to Kilojoules," scientificconverters.com. Accessed: Oct. 17, 2026. [Online]. Available: https://scientificconverters.com/energy/calories-to-kilojoules/