Need a quick gallon to liter conversion? Enter the number of gallons above, pick US or imperial, and the liters appear as you type, with the exact milliliters underneath. Liters are spelled litres in British English, and the numbers are identical. For US gallons the factor is 3.785411784 liters per gallon. Below you will find where that number comes from, worked examples, a chart, and a look at fuel economy and gas prices, where most gallon-to-liter questions begin.
A US gallon is 3.785411784 liters, and that figure is exact rather than rounded. The gallon is defined as 231 cubic inches, and the inch is defined as exactly 2.54 centimeters, so one cubic inch is 16.387064 milliliters. Multiply the two and 231 × 16.387064 gives 3,785.411784 mL, which is 3.785411784 L. An imperial gallon is defined directly in metric terms as 4.54609 liters, and the menu in the converter switches between the two.
How many liters are in a gallon of water? The same 3.7854, because liters measure volume and the substance does not matter. If you would rather work in fluid ounces, the gallon to oz converter covers that.
Liters = US gallons × 3.785411784
Liters = Imperial gallons × 4.54609
For a mental estimate with US gallons, multiply by 4 and take off about 5.4%.
How many liters is half a gallon? 0.5 × 3.785411784 = 1.8927 L. In the same way 1.5 gallons is 5.6781 L, 2.5 gallons is 9.4635 L and 3.5 gallons is 13.2489 L. You can type 1/2 or ½ as well as 0.5.
Shortcuts such as 3.8 or 4 are tempting, but the error grows with the volume. At 100 gallons:
| Factor used | Result | Difference from exact |
|---|---|---|
| 3.785411784 (exact) | 378.541 L | — |
| 3.785 | 378.500 L | −0.041 L (−0.01%) |
| 3.8 | 380.000 L | +1.459 L (+0.39%) |
| 4 | 400.000 L | +21.459 L (+5.67%) |
US gallons and imperial gallons side by side, rounded to three decimals. Each row is the gallon amount multiplied by 3.785411784 or 4.54609.
| Gallons | US gallons in liters | Imperial gallons in liters |
|---|---|---|
| 0.5 gal | 1.893 L | 2.273 L |
| 1 gal | 3.785 L | 4.546 L |
| 1.5 gal | 5.678 L | 6.819 L |
| 2 gal | 7.571 L | 9.092 L |
| 2.5 gal | 9.464 L | 11.365 L |
| 3 gal | 11.356 L | 13.638 L |
| 3.5 gal | 13.249 L | 15.911 L |
| 4 gal | 15.142 L | 18.184 L |
| 5 gal | 18.927 L | 22.730 L |
| 6 gal | 22.712 L | 27.277 L |
| 7 gal | 26.498 L | 31.823 L |
| 8 gal | 30.283 L | 36.369 L |
| 9 gal | 34.069 L | 40.915 L |
| 10 gal | 37.854 L | 45.461 L |
| 12 gal | 45.425 L | 54.553 L |
| 15 gal | 56.781 L | 68.191 L |
| 20 gal | 75.708 L | 90.922 L |
| 25 gal | 94.635 L | 113.652 L |
| 30 gal | 113.562 L | 136.383 L |
| 40 gal | 151.416 L | 181.844 L |
| 50 gal | 189.271 L | 227.305 L |
| 75 gal | 283.906 L | 340.957 L |
| 100 gal | 378.541 L | 454.609 L |
For cups, pints, quarts and metric units in one table, see the liquid measurement conversion chart.
Converting gallons to liters matters most at the pump. Three quick rules, all using the US gallon:
Miles per gallon on a British car uses the imperial gallon, so divide 282.481 by that figure instead. A car rated at 40 imperial mpg uses about 7.06 L/100 km.
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