Kilocalorie to Rydberg Converter

Energy Converter

27 units available

Decimals:

From

To

1.919379e+21

1 kcal = 1.919379e+21 Ry

Formula:

Ry = kcal × 1.919379e+21

With your value: 1 kcal = 1.919379e+21 Ry

How big is that?

Everyday references on a logarithmic scale, all expressed in kilocalorie so you can sanity-check the result.

Heartbeat (1/4.2e+3 your value)0.000239 kcal

Your value1.00 kcal

AA battery charge (2.4× your value)2.39 kcal

Slice of bread (67× your value)66.9 kcal

Daily food intake (2.0e+3× your value)2.01e+3 kcal

Litre of petrol (8.2e+3× your value)8.17e+3 kcal

Other Kilocalorie to Rydberg conversions

2 kcal to Ry 3 kcal to Ry 4 kcal to Ry 5 kcal to Ry 6 kcal to Ry 7 kcal to Ry 8 kcal to Ry

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

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

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.

Kilocalorie (kcal)

Energy

Exact conversion

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

Rydberg (Ry)

Energy

Exact conversion

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 Kilocalorie to Rydberg

To convert from Kilocalorie (kcal) to Rydberg (Ry), multiply the value by 1.919379e+21.

Formula: Ry = kcal × 1.919379e+21

Reverse: kcal = Ry × 5.210019e-22

Step-by-Step Example

Start with your value in Kilocalorie. For example: 5 kcal
Multiply by the conversion factor: 5 x 1.919379e+21
The result is: 9.596894e+21 Ry

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.

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.

Frequently Asked Questions

How many Rydberg are in 1 Kilocalorie?

There are exactly 1.919379e+21 Rydberg in 1 Kilocalorie. This means the conversion factor from Kilocalorie to Rydberg is 1.919379e+21.

What is the formula to convert Kilocalorie to Rydberg?

The formula to convert Kilocalorie to Rydberg is: Ry = kcal × 1.919379e+21. For example, to convert 10 Kilocalorie to Rydberg, you would multiply 10 by 1.919379e+21.

What is a Kilocalorie?