Gallons to Millilitres Converter
Convert US gallons to millilitres — one US gallon is exactly 3,785.41 mL. Results update as you type; exact factors shown.
One US gallon is 3,785.4118 millilitres — see the exact factor, not a rounded rule of thumb.
How the gallons to millilitres converter works
Volumes convert through the litre (exactly 1 dm³). The US gallon is exactly 3.785411784 L (231 cubic inches); the imperial gallon is exactly 4.54609 L. A US fluid ounce is 29.5735 mL, an imperial fluid ounce 28.4131 mL; a US pint is 16 US fl oz, an imperial pint 20 imperial fl oz.
Australia is fully metric under the National Measurement Act 1960; imperial units appear only in trade with the US and in older documents.
Common volume conversions
| From | To | Units |
|---|---|---|
| 0.1 US gal | 378.5412 mL | US gallons to millilitres |
| 0.25 US gal | 946.3529 mL | US gallons to millilitres |
| 0.5 US gal | 1,892.7059 mL | US gallons to millilitres |
| 1 US gal | 3,785.4118 mL | US gallon to millilitres |
| 1.5 US gal | 5,678.1177 mL | US gallons to millilitres |
| 2 US gal | 7,570.8236 mL | US gallons to millilitres |
| 3 US gal | 11,356.2354 mL | US gallons to millilitres |
| 5 US gal | 18,927.0589 mL | US gallons to millilitres |
| 10 US gal | 37,854.1178 mL | US gallons to millilitres |
| 20 US gal | 75,708.2357 mL | US gallons to millilitres |
| 50 US gal | 189,270.5892 mL | US gallons to millilitres |
| 100 US gal | 378,541.1784 mL | US gallons to millilitres |
Units in this converter and their exact factors
| Unit | Symbol | One unit in litres |
|---|---|---|
| millilitre | mL | 0.001 litre |
| litre | L | 1 litre |
| cubic metre | m³ | 1,000 litre |
| teaspoon (metric) | tsp | 0.005 litre |
| tablespoon (metric) | tbsp | 0.015 litre |
| cup (metric) | cup | 0.25 litre |
| US fluid ounce | US fl oz | 0.0295735296 litre |
| US cup | US cup | 0.2365882365 litre |
| US pint | US pt | 0.473176473 litre |
| US gallon | US gal | 3.785411784 litre |
| imperial fluid ounce | imp fl oz | 0.0284130625 litre |
| imperial pint | imp pt | 0.56826125 litre |
| imperial gallon | imp gal | 4.54609 litre |
| cubic foot | ft³ | 28.316846592 litre |
FAQFrequently asked questions about volume conversion
How many millilitres in a US gallon?
Exactly 3,785.411784.
And an imperial gallon?
4,546.09 mL — about 20% more.
What is half a gallon?
1,893 mL, close to two litres.
Why is the US gallon smaller?
It kept the old English wine gallon of 231 cubic inches; the UK redefined its gallon in 1824.
What is a gallon in litres?
3.785 L US, 4.546 L imperial.
Where these figures come from
- BIPM — The International System of Units (SI Brochure, 9th edition) — definitions of the base and derived units.
- NIST Special Publication 811 — Guide for the Use of the International System of Units — the exact conversion factors used here.
- National Measurement Institute (NMI) — Australia's national measurement authority.
Last checked: September 2026. Conversion factors are fixed by definition and do not change with tax years or regulations.