Kilocalories to Attojoules Converter
Enter the energy in kilocalories below to convert it to attojoules.
Convert Kilocalories to Attojoules
Enter a value in kilocalories (kcal) to convert to attojoules (aJ).
Kilocalorie to Attojoule Conversion Table
Table showing various kilocalorie measurements converted to attojoules. Click any preset value or arrow to load it into the converter.
| Kilocalories (kcal) | Attojoules (aJ) |
|---|---|
| 0.0000001 kcal | 4.184e+14 aJ |
| 0.0000002 kcal | 8.368e+14 aJ |
| 0.0000003 kcal | 1.2552e+15 aJ |
| 0.0000004 kcal | 1.6736e+15 aJ |
| 0.0000005 kcal | 2.092e+15 aJ |
| 0.0000006 kcal | 2.5104e+15 aJ |
| 0.0000007 kcal | 2.9288e+15 aJ |
| 0.0000008 kcal | 3.3472e+15 aJ |
| 0.0000009 kcal | 3.7656e+15 aJ |
| 0.00000001 kcal | 4.184e+13 aJ |
How to Convert Kilocalories to Attojoules
To convert kilocalories to attojoules, multiply the energy by the following conversion ratio: 4.184e+21 attojoules/kilocalorie.
Since one kilocalorie is equal to 4.184e+21 attojoules, you can use this simple formula to convert:
The energy in attojoules is equal to the energy in kilocalories multiplied by 4.184e+21.
For example, here's how to convert 5 kilocalories to attojoules using the formula above.
How Many Attojoules Are in a Kilocalorie?
There are 4.184e+21 attojoules in a kilocalorie, which is why we use this value in the formula above.
Our kilocalorie to attojoule calculator automatically converts your energy measurements with full decimal and scientific precision across US customary, imperial, and SI metric standards.
Kilocalories and attojoules are both units used to measure energy. Keep reading to learn more about each unit.
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). [1]
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.
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. [2]
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.
When converting energy between kilocalories (kcal) and attojoules (aJ), keep full floating-point precision (1 kcal = 4.184e+21 aJ; 1 aJ = 2.390057e-22 kcal) during intermediate calculations and round only the final attojoule figure to match your instrument tolerance.
More Kilocalorie & Attojoule Conversions
Need to calculate in the opposite direction? Use our attojoules to kilocalories calculator to switch your starting unit immediately. You can also explore related tools such as converting attojoules to kilocalories, converting kilocalories to kilojoules, or converting joules to calories.
Convert from Kilocalories
Frequently Asked Questions
References
- [1]NIST CODATA StandardNIST CODATA (CODATA Energy & Thermodynamic Constants)·Energy Metrology Standard — Kilocalories (kcal) to Attojoules (aJ)
- [2]NIST SP 811 SpecificationNIST SP 811 (NIST SP 811 App. B.9 (Energy, Work & Heat))·Unit Specifications: Kilocalorie (Food Calorie) (kcal) & Attojoule (aJ)
- [3]BIPM ReferenceBIPM (Derived SI Unit: Joule (J))·Conversion Factors & Mathematical Basis (kcal to aJ)