Convert 20 Gigajoule (GJ) to Millijoule (mJ).

20 Gigajoule equals 2.000000e+13 Millijoule. Multiply 20 by 1.000000e+12.

What is 20 Gigajoule in Millijoule?

20 Gigajoule equals 2.000000e+13 Millijoule.

How many Millijoules are in 1 Gigajoule?

There are exactly 1.000000e+12 Millijoules in 1 Gigajoule. This means the conversion factor from Gigajoule to Millijoule is 1.000000e+12.

What is the formula to convert Gigajoule to Millijoule?

The formula to convert Gigajoule to Millijoule is: mJ = GJ × 1.000000e+12. For example, to convert 10 Gigajoules to Millijoules, you would multiply 10 by 1.000000e+12.

What are the common uses of Gigajoule?

The Gigajoule is commonly used in energy calculations, engineering and science, education.

What is 20 Gigajoule in Millijoule?

To convert 20 Gigajoules to Millijoules, multiply by 1.000000e+12. Therefore, 20 Gigajoule (GJ) equals 2.000000e+13 Millijoule (mJ).

20 Gigajoule = 2.000000e+13 Millijoule

Worked example: converting Gigajoule to Millijoule

Step 1 — start with the formula. mJ = GJ × 1.000000e+12
Step 2 — substitute your figure. 20 GJ × 1.000000e+12
Step 3 — read the result. 20 GJ = 2.000000e+13 mJ
Step 4 — check it in reverse. GJ = mJ × 1.000000e-12 returns 20 GJ, which matches the figure you started with.

Energy Converter

27 units available

Decimals:

From

To

2.000000e+13

20 GJ = 2.000000e+13 mJ

Formula:

mJ = GJ × 1.000000e+12

With your value: 20 GJ = 2.000000e+13 mJ

How big is that?

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

Heartbeat (1/2.0e+10 your value)1.00e-9 GJ

AA battery charge (1/2.0e+6 your value)0.0000100 GJ

Slice of bread (1/7.1e+4 your value)0.000280 GJ

Daily food intake (1/2.4e+3 your value)0.00840 GJ

Litre of petrol (1/5.8e+2 your value)0.0342 GJ

Your value20.0 GJ

Other Gigajoule to Millijoule conversions

14 GJ to mJ 15 GJ to mJ 16 GJ to mJ 18 GJ to mJ 21 GJ to mJ 24 GJ to mJ 25 GJ to mJ Full Gigajoule to Millijoule converter

Gigajoule to Millijoule Conversion Table

Gigajoule (GJ)	Millijoule (mJ)
0.5	500,000,000,000
1	1.000000e+12
2	2.000000e+12
5	5.000000e+12
10	1.000000e+13
15	1.500000e+13
20	2.000000e+13
25	2.500000e+13
50	5.000000e+13
100	1.000000e+14
250	2.500000e+14
500	5.000000e+14
1000	1.000000e+15

Millijoule to Gigajoule Conversion Table

Millijoule (mJ)	Gigajoule (GJ)
0.5	5.000000e-13
1	1.000000e-12
2	2.000000e-12
5	5.000000e-12
10	1.000000e-11
15	1.500000e-11
20	2.000000e-11
25	2.500000e-11
50	5.000000e-11
100	1.000000e-10
250	2.500000e-10
500	5.000000e-10
1000	1.000000e-9

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.

Gigajoule (GJ)

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

Millijoule (mJ)

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 Gigajoule to Millijoule

To convert from Gigajoule (GJ) to Millijoule (mJ), multiply the value by 1.000000e+12.

Formula: mJ = GJ × 1.000000e+12

Reverse: GJ = mJ × 1.000000e-12

Step-by-Step Example

Start with your value in Gigajoule. For example: 5 GJ
Multiply by the conversion factor: 5 x 1.000000e+12
The result is: 5.000000e+12 mJ

Gigajoule and Millijoule Relationship

Both Gigajoule and Millijoule belong to the Metric (SI) system, making this an intra-system conversion within energy. Since 1 Gigajoule equals approximately 1.000e+12 Millijoules, the Gigajoule represents a larger unit interval than the Millijoule. Understanding the relationship between Gigajoule and Millijoule is essential for accurate calculations in physics, engineering, commerce, and daily applications.

About Gigajoule

The Gigajoule (symbol: GJ) is a recognized unit in the Metric (SI) measurement framework, utilized within energy applications for precision and standardized data representation.

Common uses of Gigajoule: energy calculations, engineering and science, education.

About Millijoule

The Millijoule (symbol: mJ) is a recognized unit in the Metric (SI) measurement framework, utilized within energy applications for precision and standardized data representation.

Common uses of Millijoule: energy calculations, engineering and science, education.

Frequently Asked Questions

What is 20 Gigajoule in Millijoule?: 20 Gigajoule equals 2.000000e+13 Millijoule.
How many Millijoules are in 1 Gigajoule?: There are exactly 1.000000e+12 Millijoules in 1 Gigajoule. This means the conversion factor from Gigajoule to Millijoule is 1.000000e+12.
What is the formula to convert Gigajoule to Millijoule?: The formula to convert Gigajoule to Millijoule is: mJ = GJ × 1.000000e+12. For example, to convert 10 Gigajoules to Millijoules, you would multiply 10 by 1.000000e+12.
What is a Gigajoule?: The Gigajoule (symbol: GJ) is a recognized unit in the Metric (SI) measurement framework, utilized within energy applications for precision and standardized data representation.
What is a Millijoule?: The Millijoule (symbol: mJ) is a recognized unit in the Metric (SI) measurement framework, utilized within energy applications for precision and standardized data representation.
What are the common uses of Gigajoule?: The Gigajoule is commonly used in energy calculations, engineering and science, education.

20 Gigajoule to Millijoule

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