Multiply fluid ounces by 29.5735
1 US fluid ounce equals 29.5735 ml exactly, derived from the US gallon (3785.41 ml ÷ 128 fl oz per gallon). 1 imperial fluid ounce equals 28.4131 ml exactly, from the imperial gallon (4546.09 ml ÷ 160 fl oz per gallon). The two gallons differ because the US adopted the older Queen Anne gallon while the UK switched to the imperial gallon in 1824. The 4% spread persists in every fluid-oz-based unit (cup, pint, quart, gallon).
Fluid ounces and millilitres both measure liquid volume, but the unit 'fl oz' itself has two definitions. The US fluid ounce equals 29.5735 ml; the imperial (UK) fluid ounce equals 28.4131 ml.
The two differ by about 4%, which sounds small but matters for cocktails, medication doses, and cosmetic-product labeling. American recipes, beverage containers, and the FDA use US fl oz. UK recipes, Australian recipes, and Commonwealth labeling use imperial fl oz.
ConvertBuddy uses the US fl oz definition (29.5735 ml) as default since it dominates online recipe content. Convert with care when sourcing recipes from UK or AU cookbooks, or when reading European cosmetic-product fill volumes.
Cocktail recipes list jiggers and fl oz. Bar tools sold in EU and Asian markets are marked ml. A standard 1.5 fl oz pour is ~44 ml; a 2 fl oz pour is ~59 ml. Convert to set up consistent pours across mixed-marking equipment.
Many liquid medications in the US ship with fl-oz markings on the bottle but dosing instructions in ml on the syringe. Misreading the unit can double or halve the dose.
US-market skincare lists ml and fl oz; European-market identical SKUs list only ml. Convert to confirm size match before buying same-product variants across regions.
Pour-over and espresso recipes from US-based baristas use fl oz; international specialty coffee uses ml or grams. Convert to lock in extraction ratios when following recipes across markets.
Customs and excise paperwork sometimes lists shipment volumes in fl oz while local distributors use litres or ml. Convert to verify shipment quantity matches purchase orders.
1 US fluid ounce equals 29.57 ml.
1 US cup equals 8 fluid ounces.