A recipe says 250 ml of milk. Your measuring jug is marked in fluid ounces. Converting ml to oz is a single division once you know the number to divide by. The Unit Converter does it instantly, but the maths is simple enough to do on paper.
The one number to remember: 29.5735
One US fluid ounce is 29.5735 millilitres. That single fact is the whole conversion — there is no second factor, because a millilitre and a fluid ounce both measure volume, and volume does not care what the liquid is. Two directions, two operations: millilitres to fluid ounces is a division, so the answer is always smaller; fluid ounces to millilitres is a multiplication, and the answer is always bigger. That is your sanity check.
ml to oz: divide by 29.5735
The formula is: fluid ounces = millilitres ÷ 29.5735. 250 ml ÷ 29.5735 = 8.453514 fl oz — the one worth memorising, because 250 ml is everywhere: a glass of milk, a small bottle of water, a portion of cream. It is just over 8 fl oz, which is one US cup, so a 250 ml measure is a cup plus a splash. 330 ml ÷ 29.5735 = 11.158639 fl oz: a standard 330 ml drinks can holds about 11.16 fl oz. 500 ml ÷ 29.5735 = 16.907028 fl oz: a half-litre bottle is just over a US pint (16 fl oz). 1000 ml (one litre) ÷ 29.5735 = 33.814057 fl oz: a litre is just over a US quart (32 fl oz) and four cups. Remember two: 250 ml is about 8.45 fl oz, a litre is about 33.81 fl oz.
oz to ml: multiply by 29.5735
The reverse formula is: millilitres = fluid ounces × 29.5735. 1 fl oz × 29.5735 = 29.5735 ml — one fluid ounce is just under 30 ml. 8 fl oz × 29.5735 = 236.588 ml: one US cup is 8 fl oz, and this is the conversion that unlocks American baking recipes, since 2 cups is 473.176 ml and half a cup is 118.294 ml. 12 fl oz × 29.5735 = 354.882 ml: a standard American drinks can. 16 fl oz × 29.5735 = 473.176 ml: a US pint is 16 fl oz — not the same as a British pint (20 imperial fl oz, about 568 ml). Check the country before you convert a pint.
Converting in the kitchen
A tablespoon is 15 ml, and 15 ÷ 29.5735 = 0.507211 fl oz — almost exactly half a fluid ounce, so two tablespoons make one fluid ounce near enough. A teaspoon is 5 ml, and 5 ÷ 29.5735 = 0.169070 fl oz, about a sixth of a fluid ounce. Measuring jugs are the other kitchen trap: a jug bought in Britain may be marked in imperial fluid ounces, where 250 ml reads about 8.80 fl oz instead of 8.45 fl oz. For baking, precision matters: pouring 8 fl oz where a recipe wants 250 ml leaves you about 13 ml short — enough to change a batter. Round to the nearest 5 ml for everyday cooking, and keep the full figure for baking.
The divide-by-30 shortcut
Dividing by 29.5735 is awkward mental arithmetic, so here is the shortcut everyone actually uses: divide by 30 instead. 250 ml ÷ 30 = 8.333 fl oz, and 1000 ml ÷ 30 = 33.333 fl oz. It is fast and needs no calculator, and it always understates the answer by 1.42%, because you divided by a bigger number than the real factor. 250 ml gives 8.333 fl oz instead of the true 8.453514 fl oz, a gap of 0.12 fl oz; a litre gives 33.333 fl oz instead of 33.814057 fl oz, a gap of 0.48 fl oz, about a tablespoon. On a single glass that error is invisible; on a 2-litre batch it is nearly 1 fl oz. Use the shortcut for rough sizes, and the exact factor — or the converter — when the quantity matters. Going the other way, multiply by 30: 8 fl oz × 30 = 240 ml, against the true 236.588 ml.
US fluid ounces vs UK imperial fluid ounces
The biggest source of wrong answers is not the arithmetic — it is using the wrong fluid ounce. The US fluid ounce is 29.5735 ml; the UK imperial fluid ounce is 28.4131 ml. They differ by about 4%: the imperial ounce is smaller, so the same volume converts to more imperial fluid ounces — 250 ml is 8.453514 US fl oz but 8.798758 imperial fl oz, and a litre is 33.814057 US fl oz but 35.195033 imperial fl oz. Match the recipe, not your location. If a recipe does not say which country it comes from, look at the other units — a US cup is 236.588 ml and a US pint is 473.176 ml, while the imperial pint is about 568 ml.
Fluid ounces are not weight ounces
A fluid ounce (fl oz) measures volume; an ounce (oz) measures weight. They share a word and nothing else, and converting between them needs a density, which depends on the ingredient. Water is the one case where the two line up: 8 fl oz of water weighs about 8 oz, because water’s density is close to 1 gram per millilitre. 8 fl oz of honey weighs roughly 11.5 oz, 8 fl oz of vegetable oil about 7.6 oz, and 8 fl oz of flour about 4.25 oz, because flour is mostly air. None of these converts with 29.5735, which is a volume-to-volume factor only. The Unit Converter keeps the two apart by category — and a recipe that says “8 oz” with no “fl” almost always means weight.
Common mistakes
- Dividing when you should multiply, or the reverse. Millilitres to fluid ounces is a division (250 ÷ 29.5735 = 8.453514 fl oz); fluid ounces to millilitres is a multiplication (8 × 29.5735 = 236.588 ml).
- Using the UK figure for a US recipe. 250 ml is 8.453514 US fl oz and 8.798758 imperial fl oz. Match the fluid ounce to the recipe’s country.
- Confusing fluid ounces with weight ounces. 8 fl oz of water weighs about 8 oz, but 8 fl oz of honey weighs roughly 11.5 oz and 8 fl oz of flour about 4.25 oz.
- Rounding too early. 250 ml ÷ 30 = 8.333 fl oz, and 8.333 × 29.5735 = 246.44 ml, not 250 ml. Round only at the end.
- Treating a cup as 250 ml. A US cup is 236.588 ml, not 250 ml. The 250 ml cup is the Australian cup, and using it adds about 13 ml to every cup, a 5.7% error.
- Forgetting that a pint is not a pint. A US pint is 16 fl oz (473.176 ml); a British pint is 20 imperial fl oz (about 568 ml). Check the country first.
Related tools
For the exact answer on any value, the Unit Converter does the division for you: pick Volume, enter the millilitres, and the result updates as you type. It is free, runs entirely in your browser, and needs no sign-in. For all of ToolZana’s free tools, start at the ToolZana home page.
The short version
To convert ml to oz, divide the millilitres by 29.5735, because 1 US fluid ounce is 29.5735 ml: 250 ml is 8.453514 fl oz, 500 ml is 16.907028 fl oz, and 1000 ml is 33.814057 fl oz. To convert oz to ml, multiply the fluid ounces by 29.5735: 1 fl oz is 29.5735 ml and 8 fl oz — one US cup — is 236.588 ml. For a rough estimate, divide by 30 instead, and remember it understates the answer by 1.42%. Watch out for the UK imperial fluid ounce (28.4131 ml) and for fluid ounces versus weight ounces. For any other value, the Unit Converter gives the exact answer in seconds.
Frequently Asked Questions
How many ml are in one fluid ounce?
One US fluid ounce is 29.5735 ml — the standard figure used in American recipes and by the Unit Converter on this site. The UK imperial fluid ounce is different — 28.4131 ml — so the same volume converts to more imperial fluid ounces: 250 ml is 8.453514 US fl oz but 8.798758 imperial fl oz.
Is 250 ml the same as 8 oz?
Nearly, but not exactly. 250 ml is 8.453514 US fluid ounces, so it is about half a fluid ounce more than 8 fl oz. 8 fl oz is one US cup, which is 236.588 ml — so if you pour 8 fl oz into a recipe that asked for 250 ml, you are about 13 ml short. For drinks and everyday cooking that gap does not matter; for baking, measure the full 250 ml rather than rounding down to a cup.
How do I convert oz to ml by hand?
Multiply the fluid ounces by 29.5735, because 1 US fluid ounce is 29.5735 ml. So 4 fl oz × 29.5735 = 118.294 ml, 8 fl oz × 29.5735 = 236.588 ml, and 12 fl oz × 29.5735 = 354.882 ml. The answer in millilitres is always bigger than the fluid ounces you started with — if it comes out smaller, you divided by mistake.
What is the fastest way to estimate ml to oz in my head?
Divide the millilitres by 30. 250 ml ÷ 30 = 8.333 fl oz, and 1000 ml ÷ 30 = 33.333 fl oz. The shortcut always understates the true answer by 1.42%, because 30 is bigger than the real factor of 29.5735 — so 250 ml is really 8.453514 fl oz, not 8.333 fl oz. Use it for a rough estimate, and the exact division, or the Unit Converter, when the quantity matters.
Why is the UK fluid ounce different from the US fluid ounce?
Because the two systems define their gallons differently. The US fluid ounce is one 128th of a US gallon, which works out at 29.5735 ml; the UK imperial fluid ounce is one 160th of an imperial gallon, which works out at 28.4131 ml. The imperial ounce is about 4% smaller, so the same volume converts to more imperial fluid ounces — a litre is 33.814057 US fl oz but 35.195033 imperial fl oz.
How many oz are in a litre?
A litre (1000 ml) is 33.814057 US fluid ounces — just over a US quart (32 fl oz) and just over four US cups. In imperial fluid ounces a litre is 35.195033 fl oz — another reason to check which fluid ounce a recipe means before converting a whole litre.
Can I use the same conversion for oil, milk and juice?
Yes. Millilitres and fluid ounces both measure volume, so the conversion factor is the same whatever the liquid is: 250 ml of oil, milk, juice or water is 8.453514 fl oz in every case. The liquid only matters when you cross from volume to weight — 8 fl oz of honey weighs roughly 11.5 oz while 8 fl oz of oil weighs about 7.6 oz — because weight depends on density.
How many ml is a cup?
One US cup is 236.588 ml, because a cup is 8 US fluid ounces and 8 × 29.5735 = 236.588 ml. Two cups is 473.176 ml, half a cup is 118.294 ml, and a quarter cup is 59.147 ml. Do not use 250 ml for a cup: 250 ml is the Australian cup, 13.412 ml bigger than a US cup, a 5.7% error on every cup in an American recipe.
How do I convert a 500 ml bottle to oz?
Divide 500 by 29.5735, which gives 16.907028 fl oz — just over a US pint (16 fl oz, 473.176 ml). A 500 ml bottle is the size most bottled water and soft drinks are sold in: half a litre is about 16.91 fl oz, a litre is about 33.81 fl oz, and a 250 ml bottle is about 8.45 fl oz.
What is the easiest way to convert ml to oz for any value?
Use the free Unit Converter. Pick the Volume category, enter the millilitres, and the result updates as you type, with the factor 1 fl oz = 29.5735 ml shown next to it so you can check the maths. It runs entirely in your browser, needs no sign-in, and also converts grams to ounces and cups to millilitres.