Femtojoule is 1e-15 joule units.
Femtojoules to Kilocalories Converter — fJ to kcal
Convert Femtojoule (fJ) to Kilocalorie (kcal) using the exact conversion factor (1 femtojoule = 2.390057e-19 kilocalorie). See the formula, worked examples, and conversion table.
Femtojoules to Kilocalories converter
Converter
Engineering Converter
Convert common stress, force, torque, power, and energy units used in engineering.
Context values
Some unit families need one extra value for a physically accurate result.
A kilocalorie is 1,000 calories.
Result = input x 1e-15 / 4184.
Energy units are compatible.
Reserved above the conversion cards and below the converter.
About Converting Femtojoules to Kilocalories
Femtojoule and Kilocalorie both measure a quantity used in structural or mechanical engineering — commonly stress, pressure, force, torque, power, or energy — where converting between the unit conventions used in different regions, industries, or equipment specifications is a routine part of design work. Specifically: Femtojoule is 1e-15 joule units, and a kilocalorie is 1,000 calories.
Formula
kilocalories = femtojoules × 2.390057e-19
This factor comes from each unit's defined relationship to the category's base unit: 1 femtojoule equals 1e-15 base units, and 1 kilocalorie equals 4184 base units, so dividing one by the other gives the direct femtojoule-to-kilocalorie factor of 2.390057e-19.
Simple example
1 fJ × 2.390057e-19 = 2.390057e-19 kcal
1 femtojoule = 2.390057e-19 kilocalories.
Real-world example
100 fJ × 2.390057e-19 = 2.390057e-17 kcal
100 femtojoules = 2.390057e-17 kilocalories.
Conversion table
| Femtojoule (fJ) | Kilocalorie (kcal) |
|---|---|
| 1 fJ | 2.390057e-19 kcal |
| 10 fJ | 2.390057e-18 kcal |
| 50 fJ | 1.195029e-17 kcal |
| 100 fJ | 2.390057e-17 kcal |
| 500 fJ | 1.195029e-16 kcal |
| 1,000 fJ | 2.390057e-16 kcal |
Reverse conversion: Kilocalorie to Femtojoule
2.390057e-19 kcal × 4.184e+18 = 0.9999998488 fJ
2.390057e-19 kilocalories = 0.9999998488 femtojoules.
femtojoules = kilocalories × 4.184e+18
For a page dedicated to this direction, see Kilocalorie to Femtojoule.
Understanding the Femtojoule (fJ)
Femtojoule is 1e-15 joule units.
Understanding the Kilocalorie (kcal)
A kilocalorie is 1,000 calories.
Reserved between the cards and the FAQ so the page stays balanced.
Frequently asked questions
How many kilocalories are in 1 femtojoule?
1 femtojoule equals 2.390057e-19 kilocalories, using the exact defined conversion factor rather than an estimate.
How do I convert femtojoule to kilocalorie?
Multiply the femtojoule value by 2.390057e-19. The converter above does this instantly to whatever precision you set.
How do I convert kilocalorie back to femtojoule?
Use the reverse factor: 1 kilocalorie equals 4.184e+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 engineering.
What is a kilocalorie?
Kilocalorie (kcal) is a unit of engineering.
Is the femtojoule to kilocalorie conversion exact?
Yes. Both femtojoule and kilocalorie are defined by fixed standards rather than physical artifacts, so the factor of 2.390057e-19 used above is exact to as many digits as you choose to display.
Why do engineering unit conventions vary so much by region and industry?
Pressure, force, and stress can be expressed in metric (pascal, newton), US customary (psi, pound-force), or older and industry-specific units (atmosphere, torr, kip) depending on the country, industry, and even the equipment manufacturer, which is why engineers routinely need to convert between them when working across specs from different sources.