mL to Oz: Milliliters to Fluid Ounces
Converting mL to oz looks like one sum with one answer. It isn't: three different fluid ounces are in everyday use and they aren't the same size. This page gives all three at once, so you can see which one your bottle, recipe or label actually means.
Common volumes
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Reference only. For liquid medicine, use the syringe, cup or dropper supplied with it and follow the dose on the label. A kitchen measure isn't a substitute for a device marked in milliliters, and this page gives no dosing guidance.
The three fluid ounces
1 imperial fluid ounce = 28.4130625 mL (exact)
1 label fluid ounce = 30 mL (21 CFR 101.9(b)(5)(viii))
The first two are exact by definition. A US gallon is exactly 231 cubic inches, which is 3.785411784 liters, and it is divided into 128 fluid ounces. An imperial gallon is exactly 4.54609 liters divided into 160. The imperial gallon is the larger of the two, but because it is cut into more pieces the imperial fluid ounce comes out smaller. The US fluid ounce is about 4.08 percent larger.
The third one is a rule rather than a measurement. For nutrition labeling the FDA defines a fluid ounce as 30 mL, alongside a teaspoon as 5 mL, a tablespoon as 15 mL and a cup as 240 mL. When the rule was written in 1993 the agency was asked to use 29.57 instead and declined, on the reasoning that both values end up printed as "1 fl oz" on the label either way.
So a bottle marked 30 mL and a bottle marked 1 fl oz aren't quite the same volume. The label ounce runs about 1.44 percent large.
Reference table
| mL | US fl oz | Imperial fl oz | Label fl oz | Where you see it |
|---|---|---|---|---|
| 5 | 0.1691 | 0.176 | 0.1667 | Teaspoon dose |
| 15 | 0.5072 | 0.5279 | 0.5 | Tablespoon |
| 100 | 3.381 | 3.52 | 3.333 | Carry-on limit |
| 240 | 8.115 | 8.447 | 8 | Label cup |
| 250 | 8.454 | 8.799 | 8.333 | Metric cup |
| 355 | 12 | 12.49 | 11.83 | US soda can |
| 500 | 16.91 | 17.6 | 16.67 | Water bottle |
| 750 | 25.36 | 26.4 | 25 | Wine bottle |
| 1000 | 33.81 | 35.2 | 33.33 | One liter |
Going the other way
| fl oz | US, mL | Imperial, mL | Label, mL |
|---|---|---|---|
| 1 | 29.5735 | 28.4131 | 30 |
| 2 | 59.1471 | 56.8261 | 60 |
| 4 | 118.294 | 113.652 | 120 |
| 8 | 236.588 | 227.304 | 240 |
| 12 | 354.882 | 340.957 | 360 |
| 16 | 473.176 | 454.609 | 480 |
| 32 | 946.353 | 909.218 | 960 |
Fluid ounces aren't ounces
A fluid ounce measures volume. An ounce measures weight. They share a name and nothing else.
They coincide only for water, and only roughly: a US fluid ounce of water weighs about 1.04 ounces, and the exact figure shifts with temperature. For anything else you need the density. A fluid ounce of honey weighs half again as much as a fluid ounce of milk, and a fluid ounce of flour isn't a sensible measurement at all, which is why baking by weight beats baking by volume. If your figure came off a scale rather than a measuring jug, use grams to ounces instead of this page.
The cup on the label isn't the cup in your cupboard
A US customary cup is 236.5882365 mL. The cup the FDA uses for nutrition labeling is 240 mL. The gap is 3.41 mL, about two thirds of a teaspoon per cup.
It is too small to matter in soup and large enough to matter in bread. If you are working from a nutrition panel rather than a recipe, the volumes on it are label volumes and carry these roundings. The cups to grams converter handles the ingredient side of the same problem.
Common questions
Is 30 mL one fluid ounce?
It depends which fluid ounce. A US fluid ounce is 29.5735295625 milliliters exactly. But for nutrition labeling the FDA defines one fluid ounce as 30 milliliters, under 21 CFR 101.9(b)(5)(viii), so a label reading 1 fl oz means 30 mL. The label ounce runs about 1.44 percent larger than the real one, which is why a 30 mL bottle and a 1 fl oz bottle aren't quite the same volume.
How many ounces is 100 mL?
100 milliliters is 3.381 US fluid ounces, or 3.520 imperial fluid ounces. Under the nutrition-label convention where a fluid ounce is 30 mL, the same volume reads as 3.333. The 100 mL figure is worth knowing because it is the carry-on liquid limit at most airports.
Are ounces and fluid ounces the same thing?
No. A fluid ounce measures volume and an ounce measures weight. They are only interchangeable for water, and even then only approximately. Converting an ounce of flour to milliliters needs the density of flour, not a volume factor, which is why this tool handles liquid volume only.
Why do US and imperial fluid ounces differ?
Because the two gallons are divided differently. The imperial gallon holds 160 imperial fluid ounces and the US gallon holds 128 US fluid ounces. The imperial gallon is the larger of the two, but because it is cut into more pieces, the imperial fluid ounce ends up smaller. The US fluid ounce is about 4.08 percent larger.
Related converters and guides
Sources
- NIST Guide to the SI, Appendix B. Source for the US gallon as exactly 231 cubic inches and the imperial gallon as exactly 4.54609 liters, from which both fluid ounces are derived.
- 21 CFR 101.9(b)(5)(viii). Source for the nutrition-label definitions: 1 fl oz means 30 mL, 1 cup means 240 mL, 1 tablespoon 15 mL, 1 teaspoon 5 mL.