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.
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.
When is this conversion used?
Converting between Imperial gallon and millilitre 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 Imperial gallon = 4,546.09 millilitre
1 millilitre = 0.001 litre
How to convert Imperial gallon to millilitre
To convert Imperial gallon to millilitre, multiply the value by 4,546.09.
To convert millilitre back to Imperial gallon, multiply by 0.00021997.
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: Imperial gallon to millilitre
| Imperial gallon | millilitre |
|---|---|
| 0.1 | 454.609 |
| 0.5 | 2,273.045 |
| 1 | 4,546.09 |
| 2 | 9,092.18 |
| 5 | 22,730.45 |
| 10 | 45,460.9 |
| 25 | 113,652.25 |
| 50 | 227,304.5 |
| 100 | 454,609 |
| 250 | 1,136,522.5 |
| 500 | 2,273,045 |
| 1,000 | 4,546,090 |
Common values
| Imperial gallon | millilitre | |
|---|---|---|
| A teaspoon | 0.00109985 Imperial gallon | 5 millilitre |
| A cup of coffee | 0.05499231 Imperial gallon | 250 millilitre |
| A water bottle | 0.10998462 Imperial gallon | 500 millilitre |
| A bathtub | 65.99077449 Imperial gallon | 300,000 millilitre |
| A swimming pool (Olympic) | 549,923.12074772 Imperial gallon | 2.500000e+09 millilitre |
Available Volume units
More Imperial gallon conversions
- Convert Imperial gallon to litre
- Convert Imperial gallon to millilitre
- Convert Imperial gallon to US gallon
- Convert Imperial gallon to cubic metre
- Convert Imperial gallon to US fluid ounce
- Convert Imperial gallon to Imperial fluid ounce
- Convert Imperial gallon to teaspoon (metric)
- Convert Imperial gallon to tablespoon (metric)
- Convert Imperial gallon to cubic centimetre