Liters to Gallons: US vs Imperial Gallons Explained
Converting liters to gallons sounds simple — until you realize there are two different gallons in common use. Pick the wrong one and you'll be off by about 20%, which is enough to matter when you're filling a fuel tank or buying paint.
Two Gallons, One Word
The US gallon equals 3.785411784 liters. The imperial (UK) gallon equals 4.54609 liters — about 20% bigger. Canada, Australia, and most of the world switched to liters decades ago, but you'll still see the imperial gallon in some older UK contexts.
Round numbers: 1 US gallon ≈ 3.79 L; 1 imperial gallon ≈ 4.55 L.
Fuel Economy Conversions
A US car rated 30 mpg gets 12.75 km per liter (or about 7.84 L/100 km). A 40 mpg UK car gets roughly 14.16 km per liter — better than the US figure suggests, because imperial gallons are larger.
Kitchen and Everyday Use
Recipes that call for 'a gallon' almost always mean US gallons in American cookbooks and imperial gallons in older British ones. When in doubt, the metric volume on the package is unambiguous.
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Frequently Asked Questions
Which gallon do oil prices use?
Oil is priced per barrel, where a barrel equals 42 US gallons (159 liters).
Is the US fluid ounce the same as the imperial one?
No — 1 US fl oz = 29.57 ml; 1 imperial fl oz = 28.41 ml.