Attojoule is 1e-18 joule units.
Attojoules to Kilocalories Converter — aJ to kcal
Convert Attojoule (aJ) to Kilocalorie (kcal) using the exact conversion factor (1 attojoule = 2.390057e-22 kilocalorie). See the formula, worked examples, and conversion table.
Attojoules to Kilocalories 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.
A kilocalorie is 1,000 calories.
Result = input x 1e-18 / 4184.
Energy uses the joule as the base unit.
Reserved above the conversion cards and below the converter.
About Converting Attojoules to Kilocalories
Attojoule and Kilocalorie both measure energy, and the conversion is especially useful for comparing nutrition labels (kilocalories) against scientific energy figures (joules). Specifically: Attojoule is 1e-18 joule units, and a kilocalorie is 1,000 calories.
Formula
kilocalories = attojoules × 2.390057e-22
This factor comes from each unit's defined relationship to the category's base unit: 1 attojoule equals 1e-18 base units, and 1 kilocalorie equals 4184 base units, so dividing one by the other gives the direct attojoule-to-kilocalorie factor of 2.390057e-22.
Simple example
1 aJ × 2.390057e-22 = 2.390057e-22 kcal
1 attojoule = 2.390057e-22 kilocalories.
Real-world example
100 aJ × 2.390057e-22 = 2.390057e-20 kcal
100 attojoules = 2.390057e-20 kilocalories.
Conversion table
| Attojoule (aJ) | Kilocalorie (kcal) |
|---|---|
| 1 aJ | 2.390057e-22 kcal |
| 10 aJ | 2.390057e-21 kcal |
| 100 aJ | 2.390057e-20 kcal |
| 500 aJ | 1.195029e-19 kcal |
| 1,000 aJ | 2.390057e-19 kcal |
| 2,000 aJ | 4.780115e-19 kcal |
Reverse conversion: Kilocalorie to Attojoule
2.390057e-22 kcal × 4.184e+21 = 0.9999998488 aJ
2.390057e-22 kilocalories = 0.9999998488 attojoules.
attojoules = kilocalories × 4.184e+21
For a page dedicated to this direction, see Kilocalorie to Attojoule.
Understanding the Attojoule (aJ)
Attojoule is 1e-18 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 attojoule?
1 attojoule equals 2.390057e-22 kilocalories, using the exact defined conversion factor rather than an estimate.
How do I convert attojoule to kilocalorie?
Multiply the attojoule value by 2.390057e-22. The converter above does this instantly to whatever precision you set.
How do I convert kilocalorie back to attojoule?
Use the reverse factor: 1 kilocalorie equals 4.184e+21 attojoules. You can also use the swap control in the converter above to flip the direction instantly.
What is a attojoule?
Attojoule (aJ) is a unit of energy.
What is a kilocalorie?
Kilocalorie (kcal) is a unit of energy.
Is the attojoule to kilocalorie conversion exact?
Yes. Both attojoule and kilocalorie are defined by fixed standards rather than physical artifacts, so the factor of 2.390057e-22 used above is exact to as many digits as you choose to display.