Convert Gallons to Liters
Convert US gallons (gal) to liters (L) instantly, with the exact formula, real worked examples, and the US-versus-Imperial gallon trap explained.
- Milliliter (mL)3,785.412
- Liter (L)3.785412
- Cubic Meter (m³)0.003785
- Gallon (US gal)1
- Cup (US cup)16
- Fluid Ounce (fl oz)128
- Hop (홉)21.03007
- Doe (되)2.103007
- Mal (말)0.210301
🔒 Unit conversions are computed in your browser.
The exact formula
One US liquid gallon equals exactly 3.785411784 liters, so to convert you multiply the gallon figure by 3.7854. The relationship is purely proportional, with no offset to add the way temperature scales require, so 2 gallons is exactly double 1 gallon: 7.5708 L. To go the other way, divide liters by 3.7854 or multiply by 0.264172. Because the factor is a fixed constant, the converter above simply scales your input; the only thing you actually control is how many decimal places you keep in the result.
Real numbers make it concrete
Worked examples help. A typical 15-gallon car tank holds 15 × 3.7854 = 56.78 L. A 55-gallon reef aquarium is 55 × 3.7854 = 208.20 L of water, worth knowing before you dose salt or medication by the liter. A 40-gallon residential water heater stores about 151.42 L, and a 5-gallon paint bucket is 18.93 L. Notice that errors scale with size: rounding the factor to 3.79 instead of 3.7854 would overstate that water heater by about 0.2 L.
The US-versus-Imperial gallon trap
The biggest pitfall is which gallon you mean. This page uses the US liquid gallon (3.7854 L). The UK/Imperial gallon is about 20% larger at 4.54609 L, and a US dry gallon (grain, produce) is 4.40488 L. A British recipe or fuel-economy figure quoted in gallons will be off by a fifth if you treat it as US. One more subtlety: liquids expand with heat, so fuel is sometimes sold as temperature-corrected 'net' gallons at 60°F. The volume-to-liter math is unaffected, but the gallon count itself may already be adjusted.
Frequently asked questions
Is 1 US gallon 3.7854 or 3.785 liters?
Both are rounded. The exact value is 3.785411784 L, defined from 231 cubic inches. 3.7854 is accurate to four decimals and is plenty for cooking, fuel, or tank sizing. Keep more digits only for large industrial volumes, where a fraction of a liter per gallon can add up to a meaningful amount.
How do I convert liters back to US gallons?
Divide by 3.7854, or multiply by 0.264172. For example, 10 L ÷ 3.7854 = 2.64 US gal, and a 1-liter bottle is about 0.264 gal. It is the exact inverse of the gallon-to-liter factor, so the two directions always agree.
Why doesn't my UK car's mpg match?
Because the UK uses the Imperial gallon (4.54609 L), not the US gallon (3.7854 L). An Imperial gallon is roughly 20% bigger, so 40 UK mpg is not 40 US mpg. Convert with the correct gallon or your fuel math will be off by about a fifth.