What next?
Volume converts, then usually gets costed or mixed.
How to use this converter
- Enter a value and its unit.
- Pick the unit to convert to.
- Read the result and equation.
US and UK gallons are not the same
A US gallon is 3.785 litres while a UK (imperial) gallon is 4.546 litres — about 20% larger. Fuel economy, recipes and drink sizes all depend on which gallon you mean, so this converter lists both explicitly.
Cooking units (cup, tablespoon, teaspoon) here use US definitions. They vary between countries, so for baking a kitchen scale is always more reliable than volume.
What your result means
Volume conversions are cubed, which catches people out even more often than area. A metre is about 3.28 feet, but a cubic metre is 35.3 cubic feet. Doubling every dimension of a container multiplies its volume by eight, not by two.
Then there is the gallon problem. A US liquid gallon is 3.785 litres and an imperial (UK) gallon is 4.546 litres — about 20% larger — and the same split runs through pints, quarts and fluid ounces. A recipe, a fuel-economy figure or a tank capacity is meaningless until you know which side of the Atlantic it came from, so check the source before trusting the number.
Why this one is different
US and UK gallons sit in the same grid, one above the other, and they differ by about a fifth — 3.785 litres against 4.546. Recipes, fuel economy and drum sizes all use the word "gallon" without saying which, so seeing both at once is what stops a fifth of the volume going missing.
Volume is where cooking, chemistry and commerce disagree
A cup is 240 ml in the United States, 250 ml as a metric cup in Australia and much of Europe, and 284 ml in older British recipes. A US pint is 473 ml and a UK pint is 568 ml — a 20 percent difference on the same word, which is why an American recipe scaled with a British measuring jug comes out visibly wrong.
Converting volume to weight needs the ingredient's density, and for baking the variation is enormous: a litre of water is 1 kg, of plain flour about 0.53 kg, of honey about 1.42 kg. This is why serious baking recipes give weights. Scooping flour compacts it by up to 20 percent depending on technique, so two cooks measuring "one cup" can differ by a fifth of the flour in the recipe.
Outside the kitchen the useful anchor is that a cubic metre is exactly 1,000 litres, and a cubic metre of water weighs a tonne. That single fact sizes water tanks, estimates pond volumes and sanity-checks any figure quoted in cubic metres before you order it.
Frequently asked questions
How many millilitres are in a litre?＋
Exactly 1,000. A litre is defined as 1,000 cubic centimetres, and one cubic centimetre equals one millilitre.
Why are US and UK pints different?＋
A US pint is 473 ml and a UK pint is 568 ml. The imperial system kept a larger pint, which is why a UK pint of beer is bigger.
How do I convert volume to weight?＋
Multiply by density. Water is about 1 kg per litre, so a litre weighs a kilogram, but flour is roughly 0.53 kg per litre and honey about 1.42.
What is the difference between fluid ounces and ounces?＋
A fluid ounce measures volume, an ounce measures weight. They are only interchangeable for water, and even then only approximately.
Which cup should I use in recipes?＋
A US cup is 240 ml, a metric cup 250 ml and an old UK cup 284 ml. American recipes almost always mean the 240 ml cup.
How many litres in a cubic metre?＋
Exactly 1,000. A cubic metre of water weighs a tonne, which is a useful check when sizing tanks or pools.
Related converters
Conversion reference
The gallon is the trap: the US and imperial gallons differ by about 20%.
A UK pint is 20 imperial fluid ounces; a US pint is 16 US fluid ounces. Both are called a pint.
Worked example
A 5 US gallon container in litres:
5 × 3.785411784
= 18.93 litres
The same 5 imperial gallons would be 22.73 litres — nearly four litres more. Always check which gallon a figure means, particularly in fuel economy comparisons.
Assumptions & limitations
Volume is where unit confusion causes the most real damage:
- US and imperial units share names but not sizes: gallons, pints, quarts and fluid ounces all differ between the two systems.
- Recipe measures are especially loose — a "cup" is 236.6 ml in the US, 250 ml in Australia and not a standard measure at all in the UK.
- Dry and fluid measures are different: a US dry pint is 550.6 ml, not 473.2 ml.
- This converts volume, not mass. A litre of water weighs about 1 kg, but a litre of flour weighs roughly 0.6 kg — use a scale for baking.