Gigajoule to Millijoule Converter

Energy Converter

27 units available

Decimals:

From

To

1.000000e+12

1 GJ = 1.000000e+12 mJ

Formula:

mJ = GJ × 1.000000e+12

With your value: 1 GJ = 1.000000e+12 mJ

How big is that?

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

Heartbeat (1/1.0e+9 your value)1.00e-9 GJ

AA battery charge (1/1.0e+5 your value)0.0000100 GJ

Slice of bread (1/3.6e+3 your value)0.000280 GJ

Daily food intake (1/1.2e+2 your value)0.00840 GJ

Litre of petrol (1/29 your value)0.0342 GJ

Your value1.00 GJ

Other Gigajoule to Millijoule conversions

2 GJ to mJ 3 GJ to mJ 4 GJ to mJ 5 GJ to mJ 6 GJ to mJ 7 GJ to mJ 8 GJ to mJ

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

About Gigajoule

The gigajoule (GJ) is a unit of energy and work. One gigajoule equals 1.000000 × 10^+9 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 Millijoule

The millijoule (mJ) is a unit of energy and work. One millijoule equals 0.001 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 Millijoule are in 1 Gigajoule?

There are exactly 1.000000e+12 Millijoule 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 Gigajoule to Millijoule, you would multiply 10 by 1.000000e+12.

What is a Gigajoule?