Convert Joules to Kilojoules
1 joule (J) equals 0.001 kilojoules (kJ).
1 J = 0.001 kJ
Type in either box. Scientific notation works: 1.5e-3.
Converting a list? Use the bulk joule to kilojoule converter to paste a column from Excel.
How to Convert Joule to Kilojoule
- 1 J = 0.001 kJ
- 1 kJ = 1000 J
- Example: convert 15 J to kJ: 15 J = 15 × 0.001 kJ = 0.015 kJ
Formula
kJ = J ÷ 1000
Derivation from SI units:
- 1 J = 1 N·m = 1 W·s = 1 kg·m²·s⁻²
- 1 kJ = 10³ J
Both units are defined exactly, so the factor is exact. Joule definition: joule; Kilojoule definition: kilojoule.
Worked examples
- A reading of 250 J converts to 0.25 kJ.
250 J × 0.001 = 0.25 kJ - A value of 10000 J is 10 kJ.
10000 J × 0.001 = 10 kJ
Joule to Kilojoule conversion table
| Joules (J) | Kilojoules (kJ) |
|---|---|
| 1 J | 0.001 kJ |
| 10 J | 0.01 kJ |
| 100 J | 0.1 kJ |
| 250 J | 0.25 kJ |
| 500 J | 0.5 kJ |
| 1000 J | 1 kJ |
| 4184 J | 4.184 kJ |
| 10000 J | 10 kJ |
| 100000 J | 100 kJ |
| 1000000 J | 1000 kJ |
| 3600000 J | 3600 kJ |
Where it's used
Joules are used for physics and engineering energy balances, while kilojoules appear in nutrition labels (kJ per serving). Both measure energy, work and heat, so the conversion is a fixed factor.
Joule to other energy units
| Conversion | 1 J equals |
|---|---|
| joule to kilojoule | 0.001 kJ |
| joule to megajoule | 0.000001 MJ |
| joule to calorie | 0.2390057361 cal |
| joule to kilocalorie | 0.0002390057361 kcal |
| joule to watt-hour | 0.0002777777778 Wh |
| joule to kilowatt-hour | 2.777777778 × 10⁻⁷ kWh |
| joule to BTU | 0.0009478171203 BTU |
| joule to therm | 9.48043428 × 10⁻⁹ thm |
| joule to electronvolt | 6.241509074 × 10¹⁸ eV |
| joule to foot-pound | 0.7375621493 ft·lbf |
| joule to erg | 10000000 erg |
Frequently asked questions
How many kilojoules are in 1 joule?
1 J = 0.001 kJ.
How do I convert joules to kilojoules?
Multiply the value in J by 0.001, or divide it by 1000. For example, 15 J × 0.001 = 0.015 kJ.
Is the J to kJ conversion exact?
Yes. Both units are defined exactly, and 1 J is exactly 0.001 kJ.
Sources
- The International System of Units (SI), 9th edition (SI Brochure), Bureau International des Poids et Mesures , Table 4, coherent derived units with special names.
- 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 Joules to Kilojoules. Retrieved October 17, 2026, from https://scientificconverters.com/energy/joules-to-kilojoules/
IEEE
Scientific Converters, "Convert Joules to Kilojoules," scientificconverters.com. Accessed: Oct. 17, 2026. [Online]. Available: https://scientificconverters.com/energy/joules-to-kilojoules/