Rydberg to Kilocalorie Converter
Convert Rydberg (Ry) to Kilocalorie (kcal) instantly. 1 Ry = 5.210019e-22 kcal.
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1 Ry = 5.210019e-22 kcal
Formula:
kcal = Ry × 5.210019e-22With your value: 1 Ry = 5.210019e-22 kcal
How big is that?
Everyday references on a logarithmic scale, all expressed in rydberg so you can sanity-check the result.
Other Rydberg to Kilocalorie conversions
Rydberg to Kilocalorie Conversion Table
| Rydberg (Ry) | Kilocalorie (kcal) |
|---|---|
| 0.5 | 2.605010e-22 |
| 1 | 5.210019e-22 |
| 2 | 1.042004e-21 |
| 5 | 2.605010e-21 |
| 10 | 5.210019e-21 |
| 15 | 7.815029e-21 |
| 20 | 1.042004e-20 |
| 25 | 1.302505e-20 |
| 50 | 2.605010e-20 |
| 100 | 5.210019e-20 |
| 250 | 1.302505e-19 |
| 500 | 2.605010e-19 |
| 1000 | 5.210019e-19 |
Kilocalorie to Rydberg Conversion Table
| Kilocalorie (kcal) | Rydberg (Ry) |
|---|---|
| 0.5 | 9.596894e+20 |
| 1 | 1.919379e+21 |
| 2 | 3.838758e+21 |
| 5 | 9.596894e+21 |
| 10 | 1.919379e+22 |
| 15 | 2.879068e+22 |
| 20 | 3.838758e+22 |
| 25 | 4.798447e+22 |
| 50 | 9.596894e+22 |
| 100 | 1.919379e+23 |
| 250 | 4.798447e+23 |
| 500 | 9.596894e+23 |
| 1000 | 1.919379e+24 |
Where these values come from
Every factor on this page is traced to the document that defines it. See the full provenance dataset or our methodology.
Rydberg (Ry)
Energy
Derived from the joule (1 J = 1 kg·m²/s²). Thermochemical and IT calories, BTU and kWh are exact defined multiples.
Source: NIST Special Publication 811, Guide for the Use of the International System of Units
National Institute of Standards and Technology (US) · Reviewed 2026-07-01
Kilocalorie (kcal)
Energy
Derived from the joule (1 J = 1 kg·m²/s²). Thermochemical and IT calories, BTU and kWh are exact defined multiples.
Source: NIST Special Publication 811, Guide for the Use of the International System of Units
National Institute of Standards and Technology (US) · Reviewed 2026-07-01
How to Convert Rydberg to Kilocalorie
To convert from Rydberg (Ry) to Kilocalorie (kcal), multiply the value by 5.210019e-22.
Formula: kcal = Ry × 5.210019e-22
Reverse: Ry = kcal × 1.919379e+21
Step-by-Step Example
- Start with your value in Rydberg. For example: 5 Ry
- Multiply by the conversion factor: 5 x 5.210019e-22
- The result is: 2.605010e-21 kcal
About Rydberg
The rydberg (Ry) is a unit of energy and work. One rydberg equals 2.179872 × 10^-18 joules. UnitConvertLab converts it against every other energy unit using this exact definition, so results are reproducible to full double precision rather than rounded lookup tables.
Common uses: energy calculations, engineering and science, education.
About Kilocalorie
The kilocalorie (food Calorie) equals 1,000 calories or 4,184 joules. It is the standard unit for food energy content.
Common uses: nutrition, diet, food labeling.
Frequently Asked Questions
How many Kilocalorie are in 1 Rydberg?
There are exactly 5.210019e-22 Kilocalorie in 1 Rydberg. This means the conversion factor from Rydberg to Kilocalorie is 5.210019e-22.
What is the formula to convert Rydberg to Kilocalorie?
The formula to convert Rydberg to Kilocalorie is: kcal = Ry × 5.210019e-22. For example, to convert 10 Rydberg to Kilocalorie, you would multiply 10 by 5.210019e-22.
What is a Rydberg?
The rydberg (Ry) is a unit of energy and work. One rydberg equals 2.179872 × 10^-18 joules. UnitConvertLab converts it against every other energy unit using this exact definition, so results are reproducible to full double precision rather than rounded lookup tables.
What is a Kilocalorie?
The kilocalorie (food Calorie) equals 1,000 calories or 4,184 joules. It is the standard unit for food energy content.
What are the common uses of Rydberg?
The Rydberg is commonly used in energy calculations, engineering and science, education.
Related Energy Conversions
Cite this page
UnitConvertLab. (2026). Rydberg to Kilocalorie converter. UnitConvertLab. Retrieved from https://unitconvertlab.com/convert/rydberg-to-kilocalorie