Volume Converter – Litres, Gallons, Cups and Millilitres

How volume conversion works

All volumes are converted through litres. A litre is one cubic decimetre, so 1,000 litres make a cubic metre and 1,000 millilitres make a litre. US customary units are defined from the US gallon of exactly 3.785411784 litres: a quart is a quarter gallon, a pint is half a quart, a cup is half a pint, a fluid ounce is 1/8 cup, a tablespoon is half a fluid ounce and a teaspoon is a third of a tablespoon.

US gallons and UK gallons are different

The imperial (UK) gallon is 4.54609 litres, about 20% larger than the US gallon. Fuel prices, fuel economy and aquarium sizes from the United Kingdom use imperial gallons, while US sources use US gallons. Choose the correct one: 10 UK gallons is 45.5 litres, but 10 US gallons is only 37.9 litres.

Cups, spoons and recipes

The converter uses US customary measures: 1 cup is 236.6 ml, 1 tablespoon is 14.8 ml and 1 teaspoon is 4.93 ml. Some countries use a rounded metric cup of 250 ml, and an Australian tablespoon is 20 ml. When a recipe comes from one of those countries, the difference is small for liquids but can matter in baking. To convert cups of flour or sugar into grams, use the cooking category of the unit converter, which accounts for each ingredient’s density.

Common volume conversions

• 1 litre ≈ 0.264 US gallons ≈ 4.23 US cups
• 1 US gallon = 3.785 litres = 16 cups
• 1 cubic metre = 1,000 litres ≈ 264.2 US gallons
• 1 US fluid ounce ≈ 29.57 ml

Volume and capacity

Use cubic metres for room volume, concrete or water tanks, litres for drinks and fuel, and millilitres for medicine and cosmetics. For a tank or container, multiply its inside length, width and height in metres to get cubic metres, then convert to litres or gallons.

Sources

Conversion factors follow the SI definitions in the BIPM SI Brochure and the exact factors for US customary and imperial units in NIST Special Publication 811.