How do you convert calories to microjoules?

To convert calories (cal) to microjoules (µJ), multiply the energy in calories by 4,184,000 (microjoules = calories × 4,184,000).

What is 5 calories in microjoules?

5 calories (5 cal) is equal to 20,920,000 microjoules (20,920,000 µJ).

Which is larger, 1 gram calorie (cal) (cal) or 1 microjoule (µJ)?

One gram calorie (cal) (cal) is larger than one microjoule (µJ). Specifically, 1 cal contains 4,184,000 µJ, whereas 1 µJ is 2.390057e-7 cal.

How do I convert back from microjoules (µJ) to calories (cal)?

To reverse the calculation from µJ to cal, multiply your microjoule 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 cal to µJ results to?

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

Calories to Microjoules Converter

Enter the energy in calories below to convert it to microjoules.

Microjoules to Calories (µJ → cal)

Convert Calories to Microjoules

Enter a value in calories (cal) to convert to microjoules (µJ).

Value (cal)

From

Result

•

20,920,000.000000004microjoules

5 cal = 20,920,000.000000004 µJ

Result updates automatically

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Suggested Conversions

Reference:NIST CODATA (CODATA Energy & Thermodynamic Constants)

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Gram Calorie to Microjoule Conversion Table

Table showing various gram calorie measurements converted to microjoules. Click any preset value or arrow to load it into the converter.

Calories (cal)	Microjoules (µJ)
0.0000001 cal	0.4184 µJ
0.0000002 cal	0.8368 µJ
0.0000003 cal	1.2552 µJ
0.0000004 cal	1.6736 µJ
0.0000005 cal	2.092 µJ
0.0000006 cal	2.5104 µJ
0.0000007 cal	2.9288 µJ
0.0000008 cal	3.3472 µJ
0.0000009 cal	3.7656 µJ
0.00000001 cal	0.04184 µJ

How to Convert Calories to Microjoules

To convert calories to microjoules, multiply the energy by the following conversion ratio: 4,184,000 microjoules/gram calorie.

Since one gram calorie is equal to 4,184,000 microjoules, you can use this simple formula to convert:

microjoules = calories × 4,184,000

The energy in microjoules is equal to the energy in calories multiplied by 4,184,000.

For example, here's how to convert 5 calories to microjoules using the formula above.

microjoules = (5 cal × 4,184,000) = 20,920,000 µJ

How Many Microjoules Are in a Gram Calorie?

There are 4,184,000 microjoules in a gram calorie, which is why we use this value in the formula above.

1 cal = 4,184,000 µJ|1 µJ = 0.000000239 cal

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

Calories and microjoules are both units used to measure energy. Keep reading to learn more about each unit.

What Is a Gram Calorie?

A gram calorie is a unit of energy equal to 4.184 joules (J), the base unit for energy. Thermochemical gram calorie defined as 4.184 Joules. [1]

The gram calorie is classified as a standard unit of energy. Calories can be abbreviated as cal; for example, 1 gram calorie can be written as 1 cal.

When working with calories (cal) in formulas or technical specifications, always verify whether your target system uses SI metric, US customary, or British imperial standards.

In practice, calories (cal) are widely used across standard energy applications within international standard workflows, engineering documentation, and technical data sheets.

Learn more about calories in our Energy Converter.

What Is a Microjoule?

A microjoule is a unit of energy equal to 1/1,000,000 of a joule (0.000001 J). One-millionth of a Joule. [2]

The microjoule is classified as a metric and SI-compatible unit of energy. Microjoules can be abbreviated as µJ; for example, 1 microjoule can be written as 1 µJ.

In the metric system, "micro" is the standard SI prefix for millionths, or 10⁻⁶. This makes the microjoule (µJ) a convenient decimal multiple of the joule (J).

In practice, microjoules (µJ) 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 microjoules in our Energy Converter.

When converting energy between calories (cal) and microjoules (µJ), keep full floating-point precision (1 cal = 4,184,000 µJ; 1 µJ = 0.000000239 cal) during intermediate calculations and round only the final microjoule figure to match your instrument tolerance.

More Gram Calorie & Microjoule Conversions

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

Convert from Calories

Convert to Microjoules

Frequently Asked Questions

There are 4,184,000 microjoules (µJ) in 1 gram calorie (cal). Conversely, 1 microjoule (µJ) is equal to 2.390057e-7 calories (cal).

Energy Converter

Quick Info

Direct Factor: 1 gram calorie (cal) (cal) equals 4,184,000 microjoules (µJ).
Inverse Factor: 1 microjoule (µJ) equals 2.390057e-7 calories (cal).
Formula: microjoules = calories × 4,184,000.
Verified Precision: Anchored to official NIST SP 811 and ISO/IEC 80000 standards.

Units Comparison

Gram Calorie (cal) (cal)

Thermochemical gram calorie defined as 4.184 Joules.

Microjoule (µJ)

One-millionth 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 — Calories (cal) to Microjoules (µJ)
NIST CODATA Standard
[2]
NIST SP 811 (NIST SP 811 App. B.9 (Energy, Work & Heat))·Unit Specifications: Gram Calorie (cal) (cal) & Microjoule (µJ)
NIST SP 811 Specification
[3]
BIPM (Derived SI Unit: Joule (J))·Conversion Factors & Mathematical Basis (cal to µJ)
BIPM Reference

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