Why is a UK gallon bigger than a US gallon?

They descend from different historical standards. The US gallon was fixed at 231 cubic inches (3.785411784 litres), based on the old English wine gallon. The imperial gallon was redefined in 1824 as the volume of ten pounds of water, giving 4.54609 litres. The two were never reconciled, so an imperial gallon is roughly 20% larger.

How many millilitres are in a pint?

It depends which pint. A US liquid pint is 473.18 ml. An imperial pint, used in the UK, is 568.26 ml. That is why a UK pint of beer is noticeably larger than a US one.

Is a fluid ounce a measure of weight or volume?

Volume. A fluid ounce measures how much space a liquid occupies, whereas an ounce measures mass. They are only interchangeable for water, and even then only approximately. To convert weight, use the unit converter instead.

How do I convert litres to cubic metres?

Divide by 1000. One cubic metre holds exactly 1000 litres, because a cubic metre is a cube one metre on each side and a litre is a cube 10 cm on each side.

Which cup size does this converter use?

The volume converter uses the US customary cup of 236.588 ml, which is exactly 8 US fluid ounces. The cooking converter uses the 240 ml metric cup instead, because that is the figure most modern recipes assume.

Volume Converter - Litres, Gallons, Pints & Fluid Ounces

Volume Converter Tool

Value

From

Result

Centilitre (cl)

How volume conversion works

Every unit on this page is defined against the litre, so a conversion is a single multiplication followed by a division:

result = value × (litres per source unit) ÷ (litres per target unit)

The one thing that catches people out is that US and imperial units share names but not sizes. A US gallon is 3.785411784 litres; an imperial gallon is 4.54609 litres, about 20% larger. Pints and fluid ounces differ too, and in opposite directions: a UK pint is larger than a US pint, but a UK fluid ounce is slightly smaller than a US one, because the imperial pint holds 20 fluid ounces where the US pint holds 16. Both are listed separately here so you never have to guess.

For recipe quantities, the cooking converter uses the 240 ml metric cup and is the better tool. For engineering work in cubic measures, the unit converter covers length and area alongside volume.

Quick reference

Common volume conversions

Conversion	Result
1 litre	0.264172 US gallons
1 litre	0.219969 imperial gallons
1 US gallon	3.785411784 litres
1 imperial gallon	4.54609 litres
1 US pint	473.176473 ml
1 imperial pint	568.26125 ml
1 US fluid ounce	29.5735 ml
1 imperial fluid ounce	28.4131 ml
1 cubic metre	1000 litres
1 cubic foot	28.3168 litres

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Questions

Frequently Asked Questions

Why is a UK gallon bigger than a US gallon?: They descend from different historical standards. The US gallon was fixed at 231 cubic inches (3.785411784 litres), based on the old English wine gallon. The imperial gallon was redefined in 1824 as the volume of ten pounds of water, giving 4.54609 litres. The two were never reconciled, so an imperial gallon is roughly 20% larger.
How many millilitres are in a pint?: It depends which pint. A US liquid pint is 473.18 ml. An imperial pint, used in the UK, is 568.26 ml. That is why a UK pint of beer is noticeably larger than a US one.
Is a fluid ounce a measure of weight or volume?: Volume. A fluid ounce measures how much space a liquid occupies, whereas an ounce measures mass. They are only interchangeable for water, and even then only approximately. To convert weight, use the unit converter instead.
How do I convert litres to cubic metres?: Divide by 1000. One cubic metre holds exactly 1000 litres, because a cubic metre is a cube one metre on each side and a litre is a cube 10 cm on each side.
Which cup size does this converter use?: The volume converter uses the US customary cup of 236.588 ml, which is exactly 8 US fluid ounces. The cooking converter uses the 240 ml metric cup instead, because that is the figure most modern recipes assume.