Gallons to litres

Reembun. (2026, July 28). Gallons to litres. https://reembun.com/convert/volume/gallons-to-liters

Two different gallons

1 US gallon        = 3.785411784 litres   (exact)
1 imperial gallon  = 4.54609 litres        (exact)

The imperial gallon is about 20.2% larger. Both are exact by definition, and both are called “a gallon” in speech, which has caused genuine confusion in fuel economy comparisons, recipe conversions and shipping documents.

Measure	US	Imperial
Gallon	3.7854 l	4.5461 l
Quart	0.9464 l	1.1365 l
Pint	0.4732 l	0.5683 l
Fluid ounce	29.574 ml	28.413 ml
Fl oz per pint	16	20

Note the last two rows. The imperial fluid ounce is smaller than the US one, but there are more of them in a pint, so an imperial pint is larger. This is exactly the sort of detail that ruins a scaled recipe.

Quick reference (US gallons)

Gallons	Litres
1	3.785
2	7.571
5	18.927
10	37.854
15	56.781
20	75.708
50	189.27

Fuel economy

Miles per gallon and litres per 100 km are reciprocal, not proportional:

L/100km = 235.215 ÷ US mpg
US mpg  = 235.215 ÷ L/100km

US mpg	L/100km
15	15.7
20	11.8
25	9.4
30	7.8
40	5.9
50	4.7

Because the relationship is reciprocal, equal gains in mpg are not equal gains in fuel saved. Going from 15 to 20 mpg saves 3.9 L per 100 km; going from 40 to 45 saves only 0.7. This is the reason regulators increasingly quote consumption per distance rather than distance per volume, since it makes the actual saving legible.

Cooking measures

For kitchen work the smaller units matter more than gallons:

US measure	Millilitres
1 teaspoon	4.93
1 tablespoon	14.79
1 fluid ounce	29.57
1 cup	236.59
1 pint	473.18

Most recipes round a cup to 240 ml and a tablespoon to 15 ml, which is close enough for cooking and not close enough for baking by weight. Where precision matters, weigh rather than measure by volume.