Attojoules to Kilocalories Converter
Enter the energy in attojoules below to convert it to kilocalories.
Convert Attojoules to Kilocalories
Enter a value in attojoules (aJ) to convert to kilocalories (kcal).
Attojoule to Kilocalorie Conversion Table
Table showing various attojoule measurements converted to kilocalories. Click any preset value or arrow to load it into the converter.
| Attojoules (aJ) | Kilocalories (kcal) |
|---|---|
| 1 aJ | 2.390057e-22 kcal |
| 10 aJ | 2.390057e-21 kcal |
| 100 aJ | 2.390057e-20 kcal |
| 1,000 aJ | 2.390057e-19 kcal |
| 10,000 aJ | 2.390057e-18 kcal |
| 100,000 aJ | 2.390057e-17 kcal |
| 1,000,000 aJ | 2.390057e-16 kcal |
| 5,000,000 aJ | 1.195029e-15 kcal |
| 10,000,000 aJ | 2.390057e-15 kcal |
| 25,400,000 aJ | 6.070746e-15 kcal |
How to Convert Attojoules to Kilocalories
To convert attojoules to kilocalories, multiply the energy by the following conversion ratio: 2.390057e-22 kilocalories/attojoule.
Since one attojoule is equal to 2.390057e-22 kilocalories, you can use this simple formula to convert:
The energy in kilocalories is equal to the energy in attojoules multiplied by 2.390057e-22.
For example, here's how to convert 5 attojoules to kilocalories using the formula above.
How Many Kilocalories Are in an Attojoule?
There are 2.390057e-22 kilocalories in an attojoule, which is why we use this value in the formula above.
Our attojoule to kilocalorie calculator automatically converts your energy measurements with full decimal and scientific precision across US customary, imperial, and SI metric standards.
Attojoules and kilocalories are both units used to measure energy. Keep reading to learn more about each unit.
What Is an Attojoule?
An attojoule is a unit of energy equal to 1/999,999,999,999,999,900 of a joule (1e-18 J). 10⁻¹⁸ Joules. [1]
The attojoule is classified as a metric and SI-compatible unit of energy. Attojoules can be abbreviated as aJ; for example, 1 attojoule can be written as 1 aJ.
When working with attojoules (aJ) in formulas or technical specifications, always verify whether your target system uses SI metric, US customary, or British imperial standards.
In practice, attojoules (aJ) are widely used across fine-tolerance laboratory, analytical, and micro-scale energy measurements within SI metric workflows, engineering documentation, and technical data sheets.
What Is a Kilocalorie?
A kilocalorie is a unit of energy equal to 4,184 joules (J), the base unit for energy. Dietary Calorie equal to 1,000 small calories (4,184 Joules). [2]
The kilocalorie is classified as a standard unit of energy. Kilocalories can be abbreviated as kcal; for example, 1 kilocalorie can be written as 1 kcal.
In the metric system, "kilo" is the standard SI prefix for thousands, or 10³. This makes the kilocalorie (kcal) a convenient decimal multiple of the calorie (cal).
In practice, kilocalories (kcal) are widely used across large-scale industrial, bulk, and macro-level energy specifications within international standard workflows, engineering documentation, and technical data sheets.
When converting energy between attojoules (aJ) and kilocalories (kcal), keep full floating-point precision (1 aJ = 2.390057e-22 kcal; 1 kcal = 4.184e+21 aJ) during intermediate calculations and round only the final kilocalorie figure to match your instrument tolerance.
More Attojoule & Kilocalorie Conversions
Need to calculate in the opposite direction? Use our kilocalories to attojoules calculator to switch your starting unit immediately. You can also explore related tools such as converting kilocalories to attojoules, converting calories to kilocalories, or converting kilojoules to kilocalories.
Convert from Attojoules
Frequently Asked Questions
References
- [1]NIST CODATA StandardNIST CODATA (CODATA Energy & Thermodynamic Constants)·Energy Metrology Standard — Attojoules (aJ) to Kilocalories (kcal)
- [2]NIST SP 811 SpecificationNIST SP 811 (NIST SP 811 App. B.9 (Energy, Work & Heat))·Unit Specifications: Attojoule (aJ) & Kilocalorie (Food Calorie) (kcal)
- [3]BIPM ReferenceBIPM (Derived SI Unit: Joule (J))·Conversion Factors & Mathematical Basis (aJ to kcal)