Is a US gallon the same as an imperial gallon?

No, and the gap is large. A US liquid gallon is 3.785411784 litres and an imperial gallon is 4.54609 litres, about twenty percent more. A recipe or a fuel figure that mixes them is out by a fifth.

How many millilitres are in a cup?

It depends whose cup. A US customary cup is 236.588 ml, a US legal cup used on nutrition labels is 240 ml, and a metric cup is 250 ml. Baking by weight avoids the question entirely.

Conversionsmeasurement

Volume Converter

Volume and capacity across metric, US and imperial units. A US gallon and an imperial gallon differ by about a fifth, which is the single most expensive confusion in this dimension.

Also called: litres to gallons, ml to cups, capacity converter.

Result

0.264172

1 Litre is 0.264172 Gallon (US). The factor is 0.2641720524, and the inverse is 3.785411784. The table below gives the same value in every volume unit at once.

Conversion factor

0.2641720524

Inverse factor

3.785411784

Value in l

Converting from

Litre

Converting to

Gallon (US)

Dimension

volume

How this is calculated

The same value in every volume unit

Unit	Value
Millilitre	1,000
Litre	1
Cubic metre	0
Cubic foot	0.04
Gallon (US)	0.26
Gallon (imperial)	0.22
Quart (US)	1.06
Cup (US)	4.23

Method and background

How this is calculated

Every unit is held against the litre. The trap is that the US and imperial systems use the same words for different sizes: an imperial gallon is 4.546 litres against the US 3.785, and an imperial fluid ounce is smaller than a US one even though the gallon is larger, because the two systems divide differently.

result = value * factor_from / factor_to

k: Each unit's size in l

Worked examples

Each of these is asserted on every build. If a change to the engine ever moved one of these answers, the build would fail before the page could print it.

a US gallon in litres

Value: 1
From: Gallon (US)
To: Litre

Result3.785412

exact by definition of the US gallon as 231 cubic inches

Open this example

an imperial gallon is larger

Value: 1
From: Gallon (imperial)
To: Litre

Result4.54609

exact by the 1985 definition

Open this example

same unit both ways

Value: 5
From: Litre
To: Litre

Result5

degenerate case

Open this example

Frequently asked questions

Is a US gallon the same as an imperial gallon?: No, and the gap is large. A US liquid gallon is 3.785411784 litres and an imperial gallon is 4.54609 litres, about twenty percent more. A recipe or a fuel figure that mixes them is out by a fifth.
How many millilitres are in a cup?: It depends whose cup. A US customary cup is 236.588 ml, a US legal cup used on nutrition labels is 240 ml, and a metric cup is 250 ml. Baking by weight avoids the question entirely.