Femtojoule is 1e-15 joule units.
Femtojoules to Kilojoules Converter — fJ to kJ
Convert Femtojoule (fJ) to Kilojoule (kJ) using the exact conversion factor (1 femtojoule = 1e-18 kilojoule). See the formula, worked examples, and conversion table.
Femtojoules to Kilojoules converter
Converter
Energy Converter
Convert joules, calories, kilowatt-hours, BTU, electronvolts, therms, and mechanical work units.
Context values
Some unit families need one extra value for a physically accurate result.
Kilojoule is 1000 joule units.
Result = input x 1e-15 / 1000.
Energy uses the joule as the base unit.
Reserved above the conversion cards and below the converter.
About Converting Femtojoules to Kilojoules
Femtojoule and Kilojoule both measure energy, and the conversion is especially useful for comparing nutrition labels (kilocalories) against scientific energy figures (joules). Specifically: Femtojoule is 1e-15 joule units, and kilojoule is 1000 joule units.
Formula
kilojoules = femtojoules × 1e-18
This factor comes from each unit's defined relationship to the category's base unit: 1 femtojoule equals 1e-15 base units, and 1 kilojoule equals 1000 base units, so dividing one by the other gives the direct femtojoule-to-kilojoule factor of 1e-18.
Simple example
1 fJ × 1e-18 = 1e-18 kJ
1 femtojoule = 1e-18 kilojoules.
Real-world example
100 fJ × 1e-18 = 1e-16 kJ
100 femtojoules = 1e-16 kilojoules.
Conversion table
| Femtojoule (fJ) | Kilojoule (kJ) |
|---|---|
| 1 fJ | 1e-18 kJ |
| 10 fJ | 1e-17 kJ |
| 100 fJ | 1e-16 kJ |
| 500 fJ | 5e-16 kJ |
| 1,000 fJ | 1e-15 kJ |
| 2,000 fJ | 2e-15 kJ |
Reverse conversion: Kilojoule to Femtojoule
1e-18 kJ × 1e+18 = 1 fJ
1e-18 kilojoules = 1 femtojoule.
femtojoules = kilojoules × 1e+18
For a page dedicated to this direction, see Kilojoule to Femtojoule.
Understanding the Femtojoule (fJ)
Femtojoule is 1e-15 joule units.
Understanding the Kilojoule (kJ)
Kilojoule is 1000 joule units.
Reserved between the cards and the FAQ so the page stays balanced.
Frequently asked questions
How many kilojoules are in 1 femtojoule?
1 femtojoule equals 1e-18 kilojoules, using the exact defined conversion factor rather than an estimate.
How do I convert femtojoule to kilojoule?
Multiply the femtojoule value by 1e-18. The converter above does this instantly to whatever precision you set.
How do I convert kilojoule back to femtojoule?
Use the reverse factor: 1 kilojoule equals 1e+18 femtojoules. You can also use the swap control in the converter above to flip the direction instantly.
What is a femtojoule?
Femtojoule (fJ) is a unit of energy.
What is a kilojoule?
Kilojoule (kJ) is a unit of energy.
Is the femtojoule to kilojoule conversion exact?
Yes. Both femtojoule and kilojoule are defined by fixed standards rather than physical artifacts, so the factor of 1e-18 used above is exact to as many digits as you choose to display.