Need a quick gallon to ml conversion? Enter the number of gallons above, pick US or imperial, and the milliliters appear as you type, with the same volume in liters underneath. One US gallon is exactly 3,785.411784 mL, so the whole job is a single multiplication. Below you will find where that number comes from, worked examples, a chart, how to scale an “mL per gallon” label, and how many bottles a gallon fills.
A US liquid gallon is exactly 3,785.411784 milliliters, or about 3.785 liters. The figure is exact because both units trace back to the inch. The gallon is defined as 231 cubic inches, and the inch is exactly 2.54 centimeters, so one cubic inch is 16.387064 mL. Multiply 231 × 16.387064 and you land on 3,785.411784 mL. The 231-cubic-inch definition is published in NIST Handbook 44.
For most kitchen, garden and aquarium jobs, 3,785 mL is accurate enough to remember. If you would rather see the same volume in liters, the gallon to liter converter has a chart of its own.
Milliliters = US gallons × 3,785.411784
Milliliters = Imperial gallons × 4,546.09
For a mental estimate with US gallons, multiply by 3,800 and take off about 0.4%.
How many ml is half a gallon? 0.5 × 3,785.411784 = 1,892.705892 mL, or about 1,892.71 mL. A quarter gallon (one quart) is 946.35 mL, an eighth is 473.18 mL and a third is 1,261.80 mL. Going up, 1.5 gallons is 5,678.12 mL and 2.5 gallons is 9,463.53 mL. You can type 1/2 or ½ as well as 0.5.
Fertilizer, cleaning concentrate, pool chemicals and aquarium treatments are often labeled with a dose such as “15 mL per gallon.” That is a ratio, so multiply it by the number of gallons you are mixing. A 5-gallon bucket at 15 mL per gallon needs 15 × 5 = 75 mL. Check the label to see whether the gallon means the finished mix or the water you start with.
| Dose per gallon | 2 gallons | 5 gallons | 10 gallons | Share of one US gallon |
|---|---|---|---|---|
| 5 mL | 10 mL | 25 mL | 50 mL | 0.1321% |
| 10 mL | 20 mL | 50 mL | 100 mL | 0.2642% |
| 15 mL | 30 mL | 75 mL | 150 mL | 0.3963% |
| 30 mL | 60 mL | 150 mL | 300 mL | 0.7925% |
| 60 mL | 120 mL | 300 mL | 600 mL | 1.5850% |
If the label is written in fluid ounces instead, the oz to ml converter turns each ounce into milliliters first, at 29.5735 mL per US fluid ounce.
“Gallon” is not one size. The imperial gallon used in the UK is defined as 4.54609 liters, so it holds 760.68 mL more than a US gallon, about 20% extra. A UK recipe asking for 2 gallons means 9,092.18 mL, while 2 US gallons is 7,570.82 mL. Use the menu in the gallon to ml converter above to switch between them.
| Gallon | Definition | Milliliters |
|---|---|---|
| US liquid gallon | 231 cubic inches | 3,785.411784 mL |
| Imperial (UK) gallon | 4.54609 liters | 4,546.09 mL |
| US dry gallon | 268.8025 cubic inches | 4,404.88 mL |
The dry gallon applies to dry goods such as grain, not to drinks or fuel, and this converter does not use it.
US and imperial gallons side by side, rounded to two decimals. Each row is the gallon amount multiplied by 3,785.411784 or 4,546.09.
| Gallons | US gallons in mL | Imperial gallons in mL |
|---|---|---|
| 1/8 gal | 473.18 mL | 568.26 mL |
| 1/4 gal | 946.35 mL | 1,136.52 mL |
| 1/3 gal | 1,261.80 mL | 1,515.36 mL |
| 1/2 gal | 1,892.71 mL | 2,273.05 mL |
| 3/4 gal | 2,839.06 mL | 3,409.57 mL |
| 1 gal | 3,785.41 mL | 4,546.09 mL |
| 1.5 gal | 5,678.12 mL | 6,819.14 mL |
| 2 gal | 7,570.82 mL | 9,092.18 mL |
| 2.5 gal | 9,463.53 mL | 11,365.23 mL |
| 3 gal | 11,356.24 mL | 13,638.27 mL |
| 4 gal | 15,141.65 mL | 18,184.36 mL |
| 5 gal | 18,927.06 mL | 22,730.45 mL |
| 6 gal | 22,712.47 mL | 27,276.54 mL |
| 8 gal | 30,283.29 mL | 36,368.72 mL |
| 10 gal | 37,854.12 mL | 45,460.90 mL |
| 12 gal | 45,424.94 mL | 54,553.08 mL |
| 15 gal | 56,781.18 mL | 68,191.35 mL |
| 20 gal | 75,708.24 mL | 90,921.80 mL |
| 25 gal | 94,635.29 mL | 113,652.25 mL |
| 50 gal | 189,270.59 mL | 227,304.50 mL |
| 75 gal | 283,905.88 mL | 340,956.75 mL |
| 100 gal | 378,541.18 mL | 454,609.00 mL |
| 250 gal | 946,352.95 mL | 1,136,522.50 mL |
| 500 gal | 1,892,705.89 mL | 2,273,045.00 mL |
| 1,000 gal | 3,785,411.78 mL | 4,546,090.00 mL |
Milliliters measure volume, so a US gallon of water, milk, juice or fuel is always 3,785.41 mL. What changes from liquid to liquid is the weight, because 1 mL of water weighs about a gram and milk is slightly heavier. The more practical question is how many containers a gallon fills:
| Container size | Containers per gallon |
|---|---|
| 250 mL (small carton) | 15.14 |
| 330 mL (can) | 11.47 |
| 500 mL (bottle) | 7.57 |
| 750 mL (wine bottle) | 5.05 |
| 1 L (1,000 mL) | 3.79 |
| 1.5 L (1,500 mL) | 2.52 |
| 2 L (2,000 mL) | 1.89 |
So a gallon jug fills about 7.6 half-liter bottles. For the full breakdown, including common bottled-water sizes, see our guide to how many water bottles make a gallon.
All the liquid volume converters you need, in one place.
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Convert US gallons to fluid ounces for large-volume work.
Turn US gallons into cups. 1 gallon is exactly 16 cups.
Convert fluid ounces to cubic centimeters, common in medical dosing.