Convert Kilojoules to Joules
1 kilojoule (kJ) equals 1000 joules (J).
1 kJ = 1000 J
Type in either box. Scientific notation works: 1.5e-3.
Converting a list? Use the bulk kilojoule to joule converter to paste a column from Excel.
How to Convert Kilojoule to Joule
- 1 kJ = 1000 J
- 1 J = 0.001 kJ
- Example: convert 15 kJ to J: 15 kJ = 15 × 1000 J = 15000 J
Formula
J = kJ × 1000
Derivation from SI units:
- 1 kJ = 10³ J
- 1 J = 1 N·m = 1 W·s = 1 kg·m²·s⁻²
Both units are defined exactly, so the factor is exact. Kilojoule definition: kilojoule; Joule definition: joule.
Worked examples
- A reading of 100 kJ converts to 100000 J.
100 kJ × 1000 = 100000 J - A value of 1000 kJ is 1000000 J.
1000 kJ × 1000 = 1000000 J
Kilojoule to Joule conversion table
| Kilojoules (kJ) | Joules (J) |
|---|---|
| 1 kJ | 1000 J |
| 4.184 kJ | 4184 J |
| 10 kJ | 10000 J |
| 50 kJ | 50000 J |
| 100 kJ | 100000 J |
| 250 kJ | 250000 J |
| 500 kJ | 500000 J |
| 840 kJ | 840000 J |
| 1000 kJ | 1000000 J |
| 2000 kJ | 2000000 J |
| 8700 kJ | 8700000 J |
| 10000 kJ | 10000000 J |
Where it's used
Kilojoules are used for nutrition labels (kJ per serving), while joules appear in physics and engineering energy balances. Both measure energy, work and heat, so the conversion is a fixed factor.
Kilojoule to other energy units
| Conversion | 1 kJ equals |
|---|---|
| kilojoule to joule | 1000 J |
| kilojoule to megajoule | 0.001 MJ |
| kilojoule to calorie | 239.0057361 cal |
| kilojoule to kilocalorie | 0.2390057361 kcal |
| kilojoule to watt-hour | 0.2777777778 Wh |
| kilojoule to kilowatt-hour | 0.0002777777778 kWh |
| kilojoule to BTU | 0.9478171203 BTU |
| kilojoule to therm | 0.00000948043428 thm |
| kilojoule to electronvolt | 6.241509074 × 10²¹ eV |
| kilojoule to foot-pound | 737.5621493 ft·lbf |
| kilojoule to erg | 10000000000 erg |
Frequently asked questions
How many joules are in 1 kilojoule?
1 kJ = 1000 J.
How do I convert kilojoules to joules?
Multiply the value in kJ by 1000. For example, 15 kJ × 1000 = 15000 J.
Is the kJ to J conversion exact?
Yes. Both units are defined exactly, and 1 kJ is exactly 1000 J.
Sources
- The International System of Units (SI), 9th edition (SI Brochure), Bureau International des Poids et Mesures , Table 7, SI prefixes.
- The International System of Units (SI), 9th edition (SI Brochure), Bureau International des Poids et Mesures , Table 4, coherent derived units with special names.
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 Kilojoules to Joules. Retrieved October 17, 2026, from https://scientificconverters.com/energy/kilojoules-to-joules/
IEEE
Scientific Converters, "Convert Kilojoules to Joules," scientificconverters.com. Accessed: Oct. 17, 2026. [Online]. Available: https://scientificconverters.com/energy/kilojoules-to-joules/