How do you convert kilocalories to millijoules?

To convert kilocalories (kcal) to millijoules (mJ), multiply the energy in kilocalories by 4,184,000 (millijoules = kilocalories × 4,184,000).

What is 5 kilocalories in millijoules?

5 kilocalories (5 kcal) is equal to 20,920,000 millijoules (20,920,000 mJ).

Which is larger, 1 kilocalorie (food calorie) (kcal) or 1 millijoule (mJ)?

One kilocalorie (food calorie) (kcal) is larger than one millijoule (mJ). Specifically, 1 kcal contains 4,184,000 mJ, whereas 1 mJ is 2.390057e-7 kcal.

How do I convert back from millijoules (mJ) to kilocalories (kcal)?

To reverse the calculation from mJ to kcal, multiply your millijoule value by the inverse factor 2.390057e-7 (or divide by 4,184,000). You can also click the Swap button in the tool above to flip directions in one click.

How many decimal places should I round kcal to mJ results to?

For everyday comparisons and quick estimates, rounding to 2 decimal places is usually sufficient (for example, 5 kcal ≈ 20,920,000.00 mJ). For engineering, laboratory, or machining specifications, select 4 or 6 decimals—or Scientific (10ⁿ) mode—in the calculator toolbar above.

Kilocalories to Millijoules Converter

Enter the energy in kilocalories below to convert it to millijoules.

Millijoules to Kilocalories (mJ → kcal)

Convert Kilocalories to Millijoules

Enter a value in kilocalories (kcal) to convert to millijoules (mJ).

Value (kcal)

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Result

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20,920,000millijoules

5 kcal = 20,920,000 mJ

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Suggested Conversions

Reference:NIST CODATA (CODATA Energy & Thermodynamic Constants)

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Kilocalorie to Millijoule Conversion Table

Table showing various kilocalorie measurements converted to millijoules. Click any preset value or arrow to load it into the converter.

Kilocalories (kcal)	Millijoules (mJ)
0.0000001 kcal	0.4184 mJ
0.0000002 kcal	0.8368 mJ
0.0000003 kcal	1.2552 mJ
0.0000004 kcal	1.6736 mJ
0.0000005 kcal	2.092 mJ
0.0000006 kcal	2.5104 mJ
0.0000007 kcal	2.9288 mJ
0.0000008 kcal	3.3472 mJ
0.0000009 kcal	3.7656 mJ
0.00000001 kcal	0.04184 mJ

How to Convert Kilocalories to Millijoules

To convert kilocalories to millijoules, multiply the energy by the following conversion ratio: 4,184,000 millijoules/kilocalorie.

Since one kilocalorie is equal to 4,184,000 millijoules, you can use this simple formula to convert:

millijoules = kilocalories × 4,184,000

The energy in millijoules is equal to the energy in kilocalories multiplied by 4,184,000.

For example, here's how to convert 5 kilocalories to millijoules using the formula above.

millijoules = (5 kcal × 4,184,000) = 20,920,000 mJ

How Many Millijoules Are in a Kilocalorie?

There are 4,184,000 millijoules in a kilocalorie, which is why we use this value in the formula above.

1 kcal = 4,184,000 mJ|1 mJ = 0.000000239 kcal

Our kilocalorie to millijoule calculator automatically converts your energy measurements with full decimal and scientific precision across US customary, imperial, and SI metric standards.

Kilocalories and millijoules 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.

Learn more about kilocalories in our Energy Converter.

What Is a Millijoule?

A millijoule is a unit of energy equal to 1/1,000 of a joule (0.001 J). One-thousandth of a Joule. [2]

The millijoule is classified as a metric and SI-compatible unit of energy. Millijoules can be abbreviated as mJ; for example, 1 millijoule can be written as 1 mJ.

In the metric system, "milli" is the standard SI prefix for thousandths, or 10⁻³. This makes the millijoule (mJ) a convenient decimal multiple of the joule (J).

In practice, millijoules (mJ) are widely used across fine-tolerance laboratory, analytical, and micro-scale energy measurements within SI metric workflows, engineering documentation, and technical data sheets.

Learn more about millijoules in our Energy Converter.

When converting energy between kilocalories (kcal) and millijoules (mJ), keep full floating-point precision (1 kcal = 4,184,000 mJ; 1 mJ = 0.000000239 kcal) during intermediate calculations and round only the final millijoule figure to match your instrument tolerance.

More Kilocalorie & Millijoule Conversions

Need to calculate in the opposite direction? Use our millijoules to kilocalories calculator to switch your starting unit immediately. You can also explore related tools such as converting millijoules to kilocalories, converting kilocalories to kilojoules, or converting joules to calories.

Convert from Kilocalories

Convert to Millijoules

Frequently Asked Questions

There are 4,184,000 millijoules (mJ) in 1 kilocalorie (kcal). Conversely, 1 millijoule (mJ) is equal to 2.390057e-7 kilocalories (kcal).

Energy Converter

Quick Info

Direct Factor: 1 kilocalorie (food calorie) (kcal) equals 4,184,000 millijoules (mJ).
Inverse Factor: 1 millijoule (mJ) equals 2.390057e-7 kilocalories (kcal).
Formula: millijoules = kilocalories × 4,184,000.
Verified Precision: Anchored to official NIST SP 811 and ISO/IEC 80000 standards.

Units Comparison

Kilocalorie (Food Calorie) (kcal)

Dietary Calorie equal to 1,000 small calories (4,184 Joules).

Millijoule (mJ)

One-thousandth of a Joule.

Joule (J)

Coherent SI unit of energy and work (1 W·s = 1 N·m).

References

[1]NIST CODATA · CODATA Energy & Thermodynamic Constants
Source
[2]NIST SP 811 · NIST SP 811 App. B.9 (Energy, Work & Heat)
Source
[3]BIPM · Derived SI Unit: Joule (J)
Source

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References

NIST · BIPM · ISO

[1]
NIST CODATA (CODATA Energy & Thermodynamic Constants)·Energy Metrology Standard — Kilocalories (kcal) to Millijoules (mJ)
NIST CODATA Standard
[2]
NIST SP 811 (NIST SP 811 App. B.9 (Energy, Work & Heat))·Unit Specifications: Kilocalorie (Food Calorie) (kcal) & Millijoule (mJ)
NIST SP 811 Specification
[3]
BIPM (Derived SI Unit: Joule (J))·Conversion Factors & Mathematical Basis (kcal to mJ)
BIPM Reference

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