Ounces to mL Converter: US Fluid Ounces and Mass Ounces

Fluid ounces are not the same as ounces of weight

The word ounce covers two different units. A US fluid ounce measures volume and equals exactly 29.5735295625 milliliters, which is 1/128 of a US gallon. An avoirdupois ounce measures weight and equals exactly 28.349523125 grams, which is 1/16 of a pound. Mixing them up is the most common error on recipes, baby formula labels and airport liquids rules, so this converter separates the two with a mode selector.

Worked example: a 12 fl oz soda can. Multiply 12 by 29.5735295625 and you get 354.88 mL, shown as 354.9 mL. To convert milliliters to fluid ounces, divide by 29.5735. The same math explains the carry-on liquids limit: 3.4 fl oz is 100.55 mL, which is why containers labeled 100 mL fit the rule. See the 3-1-1 liquids checker and the liquids ounces rule page for the screening details.

For weight, multiply ounces by 28.3495 to get grams. A 2 oz snack is 56.7 g, and 16 oz makes a pound or 453.6 g. A fluid ounce of water weighs close to 1.04 ounces, so the two scales only roughly agree for water and differ widely for oil, honey or flour. British imperial fluid ounces are also different, at 28.4131 mL, so treat foreign recipes with care. Canadian and Australian packaging often uses metric, which makes the milliliter figure the safest one to trust. Pair this page with the pounds to kg converter for larger weights.

Bartenders, bakers and parents mixing formula can scan this list for the most common amounts. Reference table of US fluid ounce equivalents, plain HTML so it works without JavaScript.

Where these numbers come from

The formulas and default values in this calculator are based on:

• NIST SP 811 Appendix B8, conversion factors (nist.gov/pml/special-publication-811/nist-guide-si-appendix-b-conversion-factors/nist-guide-si-appendix-b8)
• NIST unit conversion guidance (nist.gov/pml/owm/metric-si/unit-conversion). Note: the imperial fluid ounce value (28.4131 mL) is derived from the exact imperial gallon of 4.54609 L divided by 160

This is a planning estimate, not medical, legal or immigration advice. Fees, allowances, limits and entry rules change, so confirm the figures with your airline, cruise line, customs agency or the official government source before you book or travel, and follow their rules if they differ from this page.