mL to Fluid Ounces Converter

milliliters to US fluid ounces — quick reference

The formula, worked line by line

The US fluid ounce is defined from the top down rather than the bottom up. The US liquid gallon is exactly 3.785411784 liters, a figure that itself derives from the 231 cubic inch gallon and the exact 2.54 centimeter inch fixed in 1959. Split that gallon into 128 fluid ounces and each one is exactly 29.5735295625 milliliters.

Every smaller US liquid measure falls out of the same chain. A pint is 16 fluid ounces, a cup is 8, a tablespoon is half a fluid ounce and a teaspoon is a sixth. None of those are approximations, which is why a conversion from milliliters can be quoted to as many decimals as the situation deserves without ever losing accuracy.

US fl oz = mL ÷ 29.5735295625
         = mL × 0.0338140227…
29.5735295625 = 3 785.411784 ÷ 128   (the US gallon, split 128 ways)
250 mL → 250 ÷ 29.5735295625 = 8.453506 fl oz
imperial fl oz = mL ÷ 28.4130625

Why 30 mL is close enough for a shot and not for a bake

The convenient rounding is to treat a fluid ounce as 30 mL, which runs about 1.44 percent high. On a single 30 mL pour that is under half a milliliter and no bartender in the world would notice. Across a recipe calling for 16 fluid ounces the same rounding adds nearly 7 milliliters, which starts to move the consistency of a batter.

Volume, weight, and why they will not merge

A milliliter is a unit of volume, defined as one cubic centimeter. A fluid ounce is also a unit of volume. Neither says anything about mass, and the bridge between them and the gram is density, which is a property of the specific liquid and changes with temperature as well as with the substance.

Water is the special case that causes the confusion. Near 4 degrees Celsius water is close to one gram per milliliter, so a US fluid ounce of it weighs about 29.57 grams, which is 1.04 avoirdupois ounces rather than 1.00. Every other liquid diverges further, and for flour or sugar measured by volume the gap is enormous rather than marginal.

How to use the mL to fluid ounces converter

Milliliters are printed on almost every bottle, carton and measuring jug sold outside the United States, and on plenty sold inside it. US fluid ounces are what an American recipe, an American cup measure and an American bottle label expect. This page turns one into the other with the exact factor, which is a defined number rather than an approximation.

Type the milliliters and the fluid ounces appear as you type. The tool divides by 29.5735295625, the US fluid ounce written out in full. That figure comes from the US gallon, defined as exactly 3.785411784 liters, split into 128 parts. Nothing in it is measured, so nothing in it can drift.

Drinks are where the two systems collide most visibly. A European 330 mL can is 11.16 fl oz, an American 355 mL can is 12.00 fl oz almost exactly, and the 500 mL water bottle sold worldwide is 16.91 fl oz, which is why its American label reads 16.9. A 750 mL wine bottle is 25.36 fl oz.

Kitchen quantities are the small end of the same scale. A 15 mL metric tablespoon is 0.51 fl oz, a 30 mL shot measure is 1.01 fl oz, and a 5 mL teaspoon is 0.17 fl oz. Those near-misses are why metric spoons and US spoons can be swapped in most cooking without anyone noticing, and why they cannot be swapped in a cocktail built on ratios.

The UK fluid ounce is a different size

There are two fluid ounces in circulation and they are not interchangeable. The US fluid ounce is exactly 29.5735295625 mL. The imperial fluid ounce, still used in British and Irish recipes and on some UK labels, is exactly 28.4130625 mL, derived from the imperial gallon of exactly 4.54609 liters divided by 160 rather than 128.

That makes the imperial fluid ounce about 3.92 percent smaller than the US one. The gap is small enough to ignore in a single measure and large enough to matter across a whole recipe, and it works in the confusing direction: the imperial gallon and imperial pint are both larger than their US counterparts even though the imperial fluid ounce is smaller.

The practical rule is to look at where the recipe came from before you convert. American sources, and anything written in cups, mean the US fluid ounce. British sources published before metrication, and anything quoting a pint of 20 fluid ounces, mean the imperial one. Modern British recipes usually give milliliters outright, which sidesteps the problem completely.

The cabin bag limit, in both units

Airport security is the one place almost everyone meets this conversion. The limit is set in metric at 100 mL per container, and the United States Transportation Security Administration states the same rule in its 3-1-1 liquids policy as 3.4 ounces or 100 milliliters. Those two figures are not equal, and the difference is instructive rather than dangerous.

Convert honestly and 100 mL is 3.38 US fluid ounces, so the TSA figure of 3.4 has been rounded up. Going the other way, 3.4 fl oz is 100.55 mL, half a milliliter over the metric limit. Airport screening reads the printed container size rather than measuring the contents, so a bottle labeled 100 mL passes and a 3.4 fl oz bottle passes too.

What matters at the checkpoint is the size printed on the container, not how much is left inside it. A half-empty 250 mL bottle is still a 250 mL container and will be refused, while a full 100 mL bottle will not. Buy travel bottles marked in both units if you fly between metric and US-labeled markets, because the printed figure is the one being read.

Every milliliters value, worked out

30 common milliliters figures each get their own page, with the answer at full precision, the arithmetic, what rounding costs, and the nearest real-world reference point on the scale.

Questions people ask