What is a fluid ounce? What is a millilitre?
The oz to mL Converter turns fluid ounces into millilitres. Type a number, pick US or UK, and the answer shows up as you type, with the same amount in litres and the formula underneath. That's the whole job. The one decision that matters is the ounce, because there are two of them and they aren't the same size.
The US fluid ounce
A US fluid ounce is 1/128 of a US gallon. The US gallon is defined as exactly 231 cubic inches, and an inch is exactly 2.54 cm, so one US fluid ounce is exactly 29.5735295625 mL. Nobody memorizes that. Most people round it to 29.57 mL, or to 30 when they're in a hurry. The US ounce is on American recipes, soda cans, coffee cup sizes, US baby bottles, and US nutrition labels. A US cup is 8 of them: 236.59 mL.
The UK (imperial) fluid ounce
A UK fluid ounce is 1/160 of an imperial gallon. The imperial gallon is exactly 4.54609 litres, so one UK fluid ounce is exactly 28.4130625 mL. That's about 4% smaller than the American one. You'll find it in British recipes, in older Australian and New Zealand cookbooks written before those countries went metric, and anywhere a pint means 20 fl oz instead of 16. A British pint of milk is 20 UK fl oz, or 568.26 mL.
The millilitre
A millilitre (milliliter, in American spelling) is one thousandth of a litre. It's the same volume as one cubic centimetre. It's the unit most of the world uses: bottle labels, measuring jugs, medicine syringes, and every metric recipe. A teaspoon holds about 5 mL. A litre is 1,000 mL, which is 33.81 US fl oz or 35.20 UK fl oz.
How oz to mL conversion works
It's one multiplication. The only thing you choose besides the number is which ounce you're starting from.
US: mL = fl oz × 29.5735295625
UK: mL = fl oz × 28.4130625
Divide the result by 1,000 to get litres.
Worked example: an American recipe calls for 8 fl oz of milk, and your measuring jug only shows millilitres.
- 8 × 29.5735295625 = 236.5882365 mL
- Rounded to two decimals: 236.59 mL
- In litres: 0.2366 L
That's exactly what the oz to mL Converter shows, formula line included: 8 US fl oz × 29.5735295625 = 236.59 mL. There's a Copy formula button if you need to show your work.
Now take the same 8 ounces from a British recipe: 8 × 28.4130625 = 227.30 mL. That's 9.28 mL less, roughly two teaspoons. Small for a sauce. Scale the recipe up to 40 fl oz and the gap grows to 46.42 mL, which a bread dough will notice.
Both constants are exact. Nobody measured them in a lab; they fall straight out of how each gallon is legally defined. Rounding only happens when the result is displayed: two decimals for anything 1 mL or larger, up to four decimals below that.
Common oz to mL conversions
These are the sizes people look up most, with both ounces side by side. If the thing in your hand is American, read the US column.
| Fluid ounces | US mL | UK mL | Where you'll see it |
|---|---|---|---|
| 0.5 fl oz | 14.79 | 14.21 | A US tablespoon |
| 1 fl oz | 29.57 | 28.41 | One fluid ounce |
| 1.5 fl oz | 44.36 | 42.62 | A US shot |
| 3.4 fl oz | 100.55 | 96.60 | The carry-on liquids limit |
| 4 fl oz | 118.29 | 113.65 | Half a US cup, a small baby bottle |
| 5 fl oz | 147.87 | 142.07 | A US standard glass of wine |
| 8 fl oz | 236.59 | 227.30 | A US cup |
| 10 fl oz | 295.74 | 284.13 | Half an imperial pint |
| 12 fl oz | 354.88 | 340.96 | A US soda can (labeled 355 mL) |
| 16 fl oz | 473.18 | 454.61 | A US pint |
| 16.9 fl oz | 499.79 | 480.18 | A water bottle labeled 500 mL |
| 20 fl oz | 591.47 | 568.26 | A UK pint (use the UK column) |
| 32 fl oz | 946.35 | 909.22 | A US quart |
| 33.8 fl oz | 999.59 | 960.36 | A 1-litre bottle on a US label |
| 64 fl oz | 1,892.71 | 1,818.44 | Half a US gallon |
| 128 fl oz | 3,785.41 | 3,636.87 | A US gallon |
Two rows tell the story of this whole topic. A US pint is 16 US ounces, or 473.18 mL. A UK pint is 20 UK ounces, or 568.26 mL. The British ounce is smaller, but the British pint holds four more of them, so it ends up about 20% bigger. If you've ordered a pint in London after a week in Chicago and felt like you got a bonus, you did.
The label rows are the other pattern worth knowing. A bottle that says 16.9 fl oz is a 500 mL bottle, and 16.9 is the ounce figure rounded to one decimal. The same goes for 33.8 fl oz on a litre and 3.4 fl oz on a 100 mL travel bottle. Those products were made in metric. The ounces are a translation, which is why converting them back lands a hair off a round number.
When you'll need to convert fl oz to mL
Cooking from a recipe in the other system. Your jug is marked in millilitres and the recipe is in ounces. An American pancake recipe with 12 fl oz of buttermilk needs 354.88 mL. A British trifle recipe with 10 fl oz of custard needs 284.13 mL, not the 295.74 mL you'd get from the US ounce.
Baby bottles. US bottles are marked in ounces, while a lot of feeding guidance is written in millilitres. A 4 fl oz feed is 118.29 mL, and a 6 fl oz feed is 177.44 mL. This only translates the line on the bottle. For how much powder goes in, follow the scoop instructions on the tin.
Packing for a flight. The carry-on limit is 100 mL per container. US bottles say 3.4 fl oz, which is 100.55 mL. If a bottle only lists ounces, run the number before you pack it.
Drinks. A US cocktail recipe calls for 1.5 oz of gin and your jigger is metric. That's 44.36 mL, a little under a British double of 50 mL.
Tracking water. A goal of 64 fl oz a day is 1,892.71 mL, or just under 1.9 litres. That's easier to hit with a 500 mL bottle if you know the number.
Edge cases and gotchas
If your answer looks wrong, check these first. The ounce setting is the most common cause.
Picking the wrong ounce. Most converter pages quietly assume the US ounce and never tell you. That's fine for American recipes and wrong by 4% for British ones. The oz to mL Converter starts on US and puts the UK switch right next to the input. If the recipe mentions gas marks or a 20 fl oz pint, flip it.
Weight ounces are a different unit. A 16 oz bag of flour, a 12 oz steak, and an 8 oz block of cheese are weighed, not poured. Fluid ounces measure volume. They only line up for liquids close to water. One fluid ounce of honey weighs about 42 g, nearly 1.5 ounces. For anything sold by weight, use the ounces to grams converter instead.
Why the label says 30 mL: US nutrition labeling rules let the serving-size line treat 1 fl oz as 30 mL. So a carton might say "8 fl oz (240 mL)" while the converter says 236.59 mL. The label is rounded for tidiness. The converter gives the exact figure. For medicine, use the dosing cup or syringe that came with it, not a conversion.
Round trips aren't perfectly round. 8 US fl oz is 236.5882365 mL, displayed as 236.59. Convert 236.59 mL back to ounces and you get a hair over 8. The missing 0.002 mL is just the display rounding, and no measuring jug can see it.
Blank, negative, and huge numbers. An empty box shows nothing, and 0 returns 0 mL. A negative number gets a plain message: "Fluid ounces can't be negative. Use 0 or more." The ceiling is 1 trillion fl oz. Results of a million mL or more are shown as whole numbers with commas, and anything under 0.0001 mL shows as "< 0.0001".
Related converters
The oz to mL Converter does one direction with two ounces. Fluid ounces sit in the middle of a lot of kitchen and travel math, and these tools cover the rest of it:
- Going the other direction? The mL to oz converter turns millilitres back into US fluid ounces.
- Recipes in cups? The oz to cups converter handles fluid ounces to cups, and the cooking measurement converter covers tablespoons, teaspoons, cups, and more in one place.
- Bigger volumes, like a fuel can or an aquarium, belong in the litres to gallons converter.
- Doubling a recipe before you convert it? The recipe scaler multiplies every ingredient first.
Frequently asked questions
Is oz to mL the same as fl oz to mL?
For liquids, yes. On a drink, a bottle, or a liquid recipe ingredient, "oz" is shorthand for fluid ounce, so converting fluid ounces to milliliters is exactly what the oz to mL Converter does. On dry food, "oz" usually means weight, and this converter is the wrong tool.
How many ounces are in 1 litre?
A litre is 33.81 US fluid ounces or 35.20 UK fluid ounces. That's why a 1-litre bottle sold in the US says 33.8 fl oz on the label. Half a litre, a standard water bottle, is 16.91 US fl oz.
How many mL is 16 oz?
16 US fl oz is 473.18 mL, which is a US pint and a common large coffee size. 16 UK fl oz is 454.61 mL. If you just need the US figure for a drink, 473 mL is close enough.
Why is a US cup 236.59 mL when my measuring cup says 250?
Because there are several cups. A US customary cup is 8 US fl oz, or 236.59 mL. US nutrition labels round it to 240 mL. Australia, New Zealand, and Canada commonly use a metric cup of 250 mL. For most recipes the 13 mL gap between them won't matter. For baking, use the cup the recipe was written with.
Can I convert millilitres back to UK fluid ounces?
The mL to oz converter uses the US ounce. For UK ounces, divide the millilitres by 28.4130625. For example, 500 mL ÷ 28.4130625 = 17.60 UK fl oz.
Is the conversion exact or rounded?
The math is exact. Both constants, 29.5735295625 mL for the US ounce and 28.4130625 mL for the UK ounce, come from legal definitions, not measurements. Only the display is rounded, to two decimals for results of 1 mL or more.