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.
The UK is metric for most trade and science but keeps miles, pints, stone and mpg (with the imperial gallon) in daily life.
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 Physical Laboratory (NPL) — United Kingdom's national measurement authority.
Last checked: September 2026. Conversion factors are fixed by definition and do not change with tax years or regulations.