The litre is the most common everyday volume unit worldwide, defined as exactly 1 cubic decimetre (0.001 m³). US and UK gallons differ significantly: 1 US gallon = 3.785 L, 1 UK (imperial) gallon = 4.546 L — a 20% difference that significantly affects fuel economy comparisons between American and British sources. This converter uses US customary units throughout.
Scientific and medical contexts use millilitres and litres; fluid ounces are used in US recipes and beverage labelling. The US pint (473 mL) differs from the UK pint (568 mL). For water and dilute aqueous solutions, 1 mL ≈ 1 gram; for other ingredients this relationship varies with density, making volume measurements imprecise for dry goods.
| 1 US gallon | = 3.78541 L |
| 1 UK gallon | = 4.54609 L |
| 1 US cup | = 236.588 mL |
| 1 fl oz (US) | = 29.5735 mL |
| 1 litre | = 33.814 fl oz |
| 1 quart | = 946.353 mL |