How Many Milliliters Are in a Fluid Ounce?

One U.S. fluid ounce is exactly 29.5735295625 milliliters, or about 29.57 mL. One imperial fluid ounce is exactly 28.4130625 mL, or about 28.41 mL. For a quick U.S. kitchen estimate, 30 mL is convenient, but it is not the exact customary conversion.

If you are checking a water bottle, measuring syrup, or comparing two toiletries, first look for “fl oz” on the label. That means fluid ounces, a volume measurement. An ounce measured on a scale is a different unit and cannot be converted to milliliters without information about the material.

Why there are two fluid-ounce answers

The U.S. and imperial systems use the same unit name for slightly different volumes. The NIST conversion reference lists both, rounding the U.S. fluid ounce to 29.57353 mL and the imperial fluid ounce to 28.41306 mL.

A U.S. fluid ounce is about 4.08% larger than an imperial fluid ounce. At one ounce, the difference is roughly 1.16 mL. At 32 ounces, it becomes about 37.1 mL. That is enough to matter when matching a container capacity or scaling a drink recipe.

Use the system explicitly stated by the recipe, measuring tool, or product specification. A website’s country is a clue, but imported products and copied recipes can use another convention. If the package supplies milliliters already, use that printed quantity rather than guessing which ounce it means.

Fluid ounces to milliliters chart

Both columns below are rounded to one decimal place. The charts use the exact conversion factors before rounding, rather than repeatedly multiplying by the rough 30 mL shortcut.

Fluid ounces	U.S. fluid ounces in mL	Imperial fluid ounces in mL
0.5	14.8	14.2
1	29.6	28.4
1.5	44.4	42.6
2	59.1	56.8
3	88.7	85.2
4	118.3	113.7
6	177.4	170.5
8	236.6	227.3
12	354.9	341.0
16	473.2	454.6
20	591.5	568.3
24	709.8	681.9
32	946.4	909.2

For example, 4 U.S. fl oz is approximately 118.3 mL. Four imperial fl oz is approximately 113.7 mL. A bottle sold as 120 mL is close to the U.S. amount, but those capacities are not mathematically identical.

Milliliters to fluid ounces chart

To read a metric bottle size in fluid ounces, use this reverse chart. Results are rounded to two decimal places. These are conversions of the stated volume, not promises about how much usable product a pump or dispenser will release.

Milliliters	U.S. fluid ounces	Imperial fluid ounces
15	0.51	0.53
30	1.01	1.06
50	1.69	1.76
60	2.03	2.11
100	3.38	3.52
125	4.23	4.40
150	5.07	5.28
250	8.45	8.80
330	11.16	11.61
500	16.91	17.60
750	25.36	26.40
1000	33.81	35.20

How to convert an amount not in the chart

U.S. fl oz to mL: multiply by 29.5735295625. mL to U.S. fl oz: divide by 29.5735295625. For imperial fluid ounces, use 28.4130625 in the same calculations.

Suppose a drink recipe calls for 2.5 U.S. fl oz of juice. Calculate 2.5 × 29.5735295625 = 73.93382390625 mL. Approximately 73.9 mL is the chart-style result; about 74 mL is a practical whole-milliliter measurement.

Going the other direction, a 500 mL bottle contains 500 ÷ 29.5735295625 = approximately 16.91 U.S. fl oz. That explains why a metric bottle may carry a nearby rounded ounce figure rather than a neat whole number.

Keep the original amount through your calculation and round once at the end. If you are preparing six servings, multiply the original recipe amount by six first. Rounding each small serving upward before multiplying can add more liquid than you intended.

When does 1 fluid ounce mean 30 mL?

There are two reasons to encounter 30 mL. It is a handy approximation for a U.S. customary fluid ounce, and it is also the defined value used for U.S. nutrition labeling. The FDA’s household-measure guidance specifies 30 mL per fluid ounce for that labeling purpose.

Keep the context attached to the number. A nutrition-label convention does not change the exact customary unit used in a conversion calculator. For an informal drink, the shortcut may be sufficient. For comparing capacities or checking a precise formula, calculate with the full factor and follow the original instructions.

The shortcut is about 1.44% above the exact U.S. value. At 16 fl oz, multiplying by 30 gives 480 mL, while the customary conversion gives about 473.2 mL. Neither result should be silently substituted for a product’s explicitly stated metric quantity.

Use the conversion for bottles and drinks

For a reusable bottle, compare the stated capacity in the same unit. A 500 mL bottle holds more than a 16 U.S. fl oz bottle: the latter is about 473.2 mL. Bottle height and shape alone can be misleading, especially when one design has thicker walls.

For toiletries, compare the quantity of contents rather than the outer container dimensions. If one product is labeled by weight and the other by volume, this chart alone cannot establish which contains more product. Likewise, a container’s brimful capacity may differ from its intended fill amount.

For juice, syrups, and other drink ingredients, check the jigger or small measure itself. Different tools hold different amounts. A line marked in milliliters is easier to follow than estimating a fraction of an unfamiliar ounce measure. Use a dedicated food-safe tool, not a vessel previously used for toiletries.

A fluid ounce is not an ounce of weight

Milliliters and fluid ounces describe space occupied. Weight ounces describe mass. Oil, honey, and water can fill the same volume while having different masses, so there is no universal “weight ounces to mL” multiplier.

If your recipe gives ounces by weight, use a scale or an ingredient-specific density conversion. If it gives cups, our ounces-in-a-cup guide explains that relationship, while the milliliters-in-a-cup charts distinguish customary and metric cup sizes.

The useful habit is simple: identify the unit, choose U.S. or imperial, and keep the same definition throughout. If you need a clearer measuring tool, browse small liquid measures with milliliter markings and check their capacity and smallest scale divisions.