Convert milliliters to fluid ounce (us)

fl oz = mL ÷ 29.5735, or 0.033814 fl oz per millilitre.

American shoppers regularly ask why bottled water comes in the strange size of 16.9 fluid ounces. It does not — it comes in 500 mL, a round metric size used by bottlers worldwide, and 16.9 is simply what 500 mL becomes on a US label. The same logic explains 33.8 fl oz (1 litre) and 67.6 fl oz (the 2-litre soda bottle).

Wine and spirits in the United States have been sold in metric sizes since the late 1970s, when federal rules standardised bottles on 750 mL. It replaced the "fifth" — a fifth of a US gallon, about 757 mL — so drinkers barely noticed the change. A 750 mL bottle is 25.4 fl oz, which pours five standard 5 oz glasses of wine.

Baby bottles and dosing cups are usually printed with both scales. The millilitre scale is finer and is the one to trust for medicine: the ounce marks are often spaced at ½ oz intervals, about 15 mL, which is too coarse for small doses.

Because the FDA allows it on nutrition labels: under 21 CFR 101.9, one fluid ounce means 30 mL for nutrition labeling. The exact value, used on this page, is 1/128 of the 231-cubic-inch gallon: 29.5735295625 mL, which NIST Special Publication 811, the US guide to the SI rounds to 29.57353 mL.