Volume Converter
0.26417205 gal (US)
- 1,000
- ml
- 100
- cl
- 1
- l
- 0.001
- m³
- 202.884
- tsp
- 67.628
- tbsp
- 33.814
- fl oz (US)
- 4.22675
- cup (US)
The volume converter handles 13 units and keeps US and Imperial measures strictly separate, because they are not the same size. A US gallon is 3.785 litres and an Imperial gallon is 4.546, a 20 percent difference that silently ruins any recipe or fuel calculation that assumes they match.
How it works
The two systems diverged in 1824, when Britain redefined the gallon as the volume of ten pounds of water. The US kept the older Queen Anne wine gallon. Every derived unit inherited the difference.
- US gallon: 3.785411784 litres exactly. Imperial gallon: 4.54609 litres exactly.
- US fluid ounce: 29.5735 ml. Imperial fluid ounce: 28.4131 ml, the smaller of the two.
- A US pint is 16 US fluid ounces; an Imperial pint is 20 Imperial fluid ounces.
- A US cup is 236.588 ml. The metric cup used in Australia and New Zealand is 250 ml and is not the same unit.
The fluid ounce is the trap: the Imperial one is smaller, but the Imperial pint is larger, because it contains 20 of them rather than 16.
Examples
US to Imperial gallons
Value
1
From
US gallon
To
Imperial gallon
Result
0.83267384 gal (UK)
A US gallon is about 83 percent of an Imperial one. Fuel economy quoted in US mpg is therefore about 20 percent lower than the same car quoted in UK mpg.
A US cup in millilitres
Value
1
From
US cup
To
Millilitre
Result
236.58824 ml
Not 250 ml. Australian and New Zealand recipes use a 250 ml metric cup, so following a US recipe with a metric cup adds about 6 percent to every measured ingredient.
Pints compared
Value
1
From
Imperial pint
To
US pint
Result
1.2009499 pt (US)
A UK pint is a fifth larger than a US one, which is why a pint of beer is noticeably bigger in Britain.
Frequently asked questions
Why are US and Imperial gallons different sizes?
Because Britain redefined its gallon in 1824 as the volume of ten pounds of water, while the US kept the older Queen Anne wine gallon. The US gallon is 3.785 litres and the Imperial one is 4.546, about 20 percent larger. Every derived unit, from the quart to the fluid ounce, inherited the split.
Which fluid ounce is bigger?
The US one, at 29.57 ml against the Imperial 28.41 ml. This confuses people because the Imperial pint is bigger even though its ounces are smaller. It contains 20 of them where a US pint has 16.
Is a cup 250 ml?
Only in Australia and New Zealand, which use a metric cup. A US cup is 236.588 ml and a UK recipe cup is usually 250 ml too. Following a US recipe with a metric cup adds about 6 percent to every ingredient. Enough to matter in baking.
Why keep both systems in one list rather than picking one?
Because recipes and specifications routinely mix them without saying which they mean. Having both visible makes the ambiguity obvious rather than hiding it behind a single "gallon" option that might be either.