What is millilitre?

A millilitre is a metric unit of volume equal to one thousandth of a litre. It is commonly used in medicine, cooking, laboratory measurements, and the labelling of food and beverage products.

Real-world uses

Millilitres are used for medication dosages (cough syrup, injectable solutions), cooking measurements, cosmetic product volumes, and laboratory reagent quantities. A standard medical syringe is graduated in mL, and espresso shots are typically 25–30 mL.

History

The millilitre emerged naturally from the litre with metric prefix conventions. It became essential in medicine and laboratory science where precise small-volume measurements are critical. In medical contexts, "cc" (cubic centimetre) was long used interchangeably with mL.

Common mistakes

Confusing millilitres with cubic centimetres—they are numerically equal (1 mL = 1 cm³) but conceptually different units. Also, mixing up mL with mg; one is volume, the other is mass.

What is Imperial gallon?

An Imperial gallon is a volume unit used in the United Kingdom equal to approximately 4.546 litres. It is larger than the US gallon and is commonly referenced for fuel efficiency (miles per gallon) in the UK.

Real-world uses

Imperial gallons are used in the United Kingdom, Canada (for some purposes), and several Caribbean countries. British fuel economy was historically quoted in miles per Imperial gallon. Older Commonwealth-era recipes and industrial specifications may reference Imperial gallons.

History

The Imperial gallon was established by the British Weights and Measures Act of 1824 as the volume occupied by 10 pounds of water at 62°F (≈ 17°C). It replaced several older gallon definitions including the wine gallon (retained by the US) and the ale gallon.

Common mistakes

Assuming the Imperial gallon equals the US gallon. The Imperial gallon is about 4.546 litres versus 3.785 litres for the US gallon. Converting mpg figures between the two systems without adjusting for gallon size gives misleading results.

When is this conversion used?

Converting between millilitre and Imperial gallon is common when working across metric and imperial systems, such as international trade, travel between countries with different measurement standards, or following instructions from a different region.

Worked examples

1 millilitre = 0.00021997 Imperial gallon

1 Imperial gallon = 4.54609 litre

How to convert millilitre to Imperial gallon

To convert millilitre to Imperial gallon, multiply the value by 0.00021997.

To convert Imperial gallon back to millilitre, multiply by 4,546.09.

Measurement standards

The cubic metre is the SI derived unit of volume. The litre, equal to exactly one cubic decimetre (0.001 m³), is accepted by the BIPM for use alongside SI units. Both the lowercase "l" and uppercase "L" are approved symbols for the litre.

Did you know?

An Olympic swimming pool holds 2,500 cubic metres of water — about 2.5 million litres. The Amazon River discharges roughly 209,000 cubic metres per second, enough to fill 84 Olympic pools every single second.

Quick reference: millilitre to Imperial gallon

millilitreImperial gallon
0.10.000022
0.50.00010998
10.00021997
20.00043994
50.00109985
100.00219969
250.00549923
500.01099846
1000.02199692
2500.05499231
5000.10998462
1,0000.21996925

Common values

millilitreImperial gallon
A teaspoon5 millilitre0.00109985 Imperial gallon
A cup of coffee250 millilitre0.05499231 Imperial gallon
A water bottle500 millilitre0.10998462 Imperial gallon
A bathtub300,000 millilitre65.99077449 Imperial gallon
A swimming pool (Olympic)2.500000e+09 millilitre549,923.12074772 Imperial gallon

Available Volume units

More millilitre conversions