How to Convert Kilojoules to Joules (kJ to J)
Energy conversions link food labels in kJ and kcal, SP Group bills in kWh and air-conditioner capacity in BTU. This guide shows how to convert kilojoules into joules by hand, with examples and a quick-reference table.
The conversion
To convert kilojoules to joules, multiply the value by 1,000. To go the other way, divide by the same number (or multiply by 0.001). For a quick estimate, multiply by about 1,000.
Joules = kilojoules × 1,000
Worked examples
- 3 kJ = 3,000 J
- 12.5 kJ = 12,500 J
- 75 kJ = 75,000 J
Kilojoules to Joules table
| Kilojoules | Joules |
|---|---|
| 1 kJ | 1,000 J |
| 2 kJ | 2,000 J |
| 5 kJ | 5,000 J |
| 10 kJ | 10,000 J |
| 20 kJ | 20,000 J |
| 25 kJ | 25,000 J |
| 50 kJ | 50,000 J |
| 100 kJ | 100,000 J |
| 250 kJ | 250,000 J |
| 500 kJ | 500,000 J |
| 1,000 kJ | 1,000,000 J |
Common questions
Is kJ to J exact?
The factors used here are the internationally defined values where they exist; results are rounded for display only.
How do I convert back?
Use the Joules to Kilojoules converter.
Mistakes to avoid
Multiplying when you should divide
Converting to a smaller unit gives a bigger number, and converting to a larger unit gives a smaller one. If your answer moves the wrong way, you have inverted the factor.
Mixing similar-sounding units
US and imperial gallons, pints and tons are different sizes, and decimal kilobytes differ from binary kibibytes.
Forgetting squared and cubed units
Area and volume factors are the length factor squared or cubed, so 1 m² is about 10.76 sq ft, not 3.28.
Background
Writing the units next to every number while you work is the simplest way to avoid mistakes. If the units do not cancel to leave the one you want, the calculation is set up wrongly.
For everyday use, three or four significant figures are usually enough. Engineering, science and trade documents may need more, and rounding should happen only at the end of a calculation.
Singapore adopted the metric system in the 1970s, replacing imperial units and traditional Chinese measures in most official uses. Metric units are now standard in schools, trade and government, but older units survive in property, markets and imported goods.
For any value, use the Kilojoules to Joules Converter or browse all energy converters.
Run your own numbers: Kilojoules to Joules Converter