Volume Converter (L, gallons, ml, cups)

Convert between litres, millilitres, gallons, pints, cups and spoons in either direction, with the exact factor shown under every answer. US and UK measures are listed separately, because a US gallon and a UK gallon are genuinely different amounts — mixing them up is where most volume mistakes come from.

How to use it

Pick your unitsChoose what you are converting from and to. US and UK versions are named explicitly, so you always know which one you have.
Type the amountThe answer appears as you type. Use Swap to flip the direction.
Check the factorThe line under the result shows the exact factor used, so you can sanity-check the answer.

One word, several sizes

Volume is the messiest of the everyday measures, because the same names mean different amounts in different countries. The US gallon (3.785 L) and the imperial gallon (4.546 L) are a fifth apart. The pints differ the same way. Even the fluid ounce differs by 4%. A converter that just says "gallon" is making a guess on your behalf — this one names the system on every unit, so the guess is never silent.

All of the factors are exact by definition, not measured. The US system chains down from the 1959 inch: a gallon is 231 cubic inches, which makes it exactly 3.785411784 litres, and everything smaller divides from there in whole numbers — 4 quarts, 8 pints, 16 cups, 128 fluid ounces. The imperial gallon was fixed at exactly 4.54609 litres in 1985.

Kitchen conversions

The most common use for a volume converter is a recipe written in someone else's units. The chain worth memorising: 1 US cup = 16 tablespoons = 48 teaspoons = 236.6 ml. Half a cup is 118 ml, a quarter cup is 59 ml. Going the other way, 100 ml is just under half a cup (0.42), and a litre is about 4¼ cups.

One honest limitation: volume-to-weight conversion needs to know the ingredient. A cup of flour is about 120 g while a cup of sugar is about 200 g, so no unit converter can turn "grams of flour" into cups correctly. When a recipe gives weights, a kitchen scale beats any conversion.

Fuel, engines and aquariums

The other places volume shows up daily: fuel economy (where the two gallons cause real confusion between US and UK mpg figures), engine displacement (litres vs cubic inches — a 5.0 L engine is 302 cubic inches), and tank sizes for aquariums and water butts, where US product listings in gallons meet European tape measures in litres.

Whatever you type stays on your device, and the tool keeps working offline once loaded.

Questions people ask

How many millilitres in a cup?

A US cup is exactly 236.588 ml. Recipes from the US mean this cup. A metric cup, used in Australian recipes, is 250 ml — if a recipe seems slightly off, this difference is often why.

Why are there two gallons?

The US gallon is 231 cubic inches — about 3.785 litres. The UK (imperial) gallon is defined as exactly 4.54609 litres, roughly 20% bigger. Same word, different amounts, and fuel economy figures are the classic place the confusion bites: 40 miles per US gallon is about 48 miles per UK gallon.

Are US and UK fluid ounces the same?

No — they differ by about 4%. A US fluid ounce is 29.57 ml, a UK fluid ounce is 28.41 ml. Small enough to look like rounding, big enough to matter in a cocktail or a bake.

How many teaspoons in a tablespoon?

Three, in US kitchen measure. A tablespoon is also half a fluid ounce, and sixteen tablespoons make a cup — the whole US kitchen system chains together in whole numbers.

Can I convert grams to millilitres here?

Only for water, where 1 g = 1 ml. For anything else the answer depends on density — a millilitre of flour weighs about half what a millilitre of honey does — so an honest volume converter cannot do it. Use a recipe-specific chart for ingredients.

Are the results rounded?

Only the display. The maths runs at full precision on exact defined factors, so converting back and forth returns your original number.