Energy / J → kJ
Convert Joules to Kilojoules
Convert work, heat, and stored energy using joules as the base. Convert Joules (J) to Kilojoules (kJ). Find the formula, worked examples, unit definitions, and practical guidance below.
Reverse: Kilojoules to Joules →
How to convert joules to kilojoules
Calories use the thermochemical definition. Btu use the International Table definition. Food Calories are kilocalories, not single calories.
Use x for the value in J, b for the intermediate value in J, and y for the result in kJ.
kJ = J ÷ 1000
Worked examples
10 J ≈ 0.01 kJ
Step 1: (10 × 1) ≈ 10 J.
Step 2: 10 ÷ 1000 ≈ 0.01 kJ.20 J ≈ 0.02 kJ
Step 1: (20 × 1) ≈ 20 J.
Step 2: 20 ÷ 1000 ≈ 0.02 kJ.
Results are rounded to 12 significant digits. Converting units does not increase the precision of the original measurement. Very large or small values outside JavaScript’s finite numeric range are rejected.
About Joules
Joules (J) measures energy under the conventions above. The base value in J is (x × 1), where x is the numerical value in J. Factors shown here are rounded for display; calculations use the stored factor.
About Kilojoules
Kilojoules (kJ) measures energy under the conventions above. The base value in J is (x × 1000), where x is the numerical value in kJ. Factors shown here are rounded for display; calculations use the stored factor.
Definitions and sources
Carry the same physical assumptions into subsequent physics calculations.
Joules to kilojoules reference table
| Joules (J) | Kilojoules (kJ) |
|---|---|
| 1 | 0.001 |
| 5 | 0.005 |
| 10 | 0.01 |
| 25 | 0.025 |
| 50 | 0.05 |
| 100 | 0.1 |
| 1000 | 1 |
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