Fluid Ounces to Milliliters Converter

How Fluid Ounces to Milliliters Conversion Works

A US fluid ounce is a unit of volume equal to approximately 29.5735 milliliters. This conversion is one of the most commonly needed in cooking, beverage production, and medication dosing. The fluid ounce is used primarily in the United States, while milliliters are the standard volume unit in the metric system used by over 95% of the world's countries.

According to the National Institute of Standards and Technology (NIST), the US fluid ounce is defined as exactly 1/128 of a US gallon, and the US gallon equals exactly 3.785411784 liters. This gives 1 US fl oz = 3,785.411784 / 128 = 29.57353 mL. The FDA rounds this to 30 mL per fluid ounce for nutrition labeling purposes.

It is critical to distinguish between US and UK (Imperial) fluid ounces. A UK fluid ounce is 28.4131 mL -- about 4.1% smaller than its US counterpart. This means a British recipe calling for 8 fl oz gives 227.3 mL, while a US recipe with 8 fl oz gives 236.6 mL. Our Cooking Converter handles both systems, while our Volume Converter covers all volume units.

The Fluid Ounces to Milliliters Formula

The conversion formulas are:

Milliliters = US Fluid Ounces x 29.5735

US Fluid Ounces = Milliliters / 29.5735

For UK (Imperial) fluid ounces:

Milliliters = UK Fluid Ounces x 28.4131

The US factor derives from: 1 US gallon = 3,785.411784 mL exactly, divided by 128 fluid ounces = 29.57353 mL per fl oz.

Worked example: A cocktail recipe calls for 2.5 fl oz of gin. In milliliters: 2.5 x 29.5735 = 73.93 mL. A standard 750 mL bottle of spirits contains 750 / 29.5735 = 25.36 fl oz, which makes about 16 cocktails with 1.5 fl oz (standard shot) per drink.

Key Terms You Should Know

• US Fluid Ounce (fl oz) -- A unit of volume equal to 1/128 of a US gallon or approximately 29.5735 mL. There are 8 fluid ounces in a US cup and 16 in a US pint.
• UK (Imperial) Fluid Ounce -- A unit of volume equal to 1/160 of an Imperial gallon or approximately 28.4131 mL. There are 20 Imperial fluid ounces in an Imperial pint (vs. 16 in a US pint).
• Milliliter (mL) -- A metric unit of volume equal to 1/1,000 of a liter or 1 cubic centimeter (cc). The standard volume unit for beverages, medications, and cooking in most of the world.
• Liter (L) -- Equal to 1,000 mL. A US quart (32 fl oz) is approximately 946 mL, slightly less than a liter. A UK quart (40 fl oz) is approximately 1,137 mL, slightly more than a liter.
• Cup -- A US cup equals 8 US fluid ounces (236.59 mL). A metric cup (used in Australia and some other countries) equals exactly 250 mL (8.45 fl oz).

Fluid Ounces to Milliliters Reference Table

Common volume conversions based on the US fluid ounce definition per NIST.

Practical Examples

Travel with liquids: TSA allows each liquid container to hold a maximum of 3.4 fl oz (100 mL) in carry-on luggage. A typical travel-size toiletry bottle holds 3 fl oz (88.72 mL), which is within the limit. A standard travel shampoo from the hotel is usually 30-50 mL (1-1.7 fl oz). Knowing the fl oz to mL conversion ensures you stay within TSA guidelines.

Baby formula preparation: Many infant formula instructions specify amounts in fluid ounces (e.g., "prepare 4 fl oz per feeding"). In milliliters: 4 x 29.57 = 118.3 mL. Baby bottles sold internationally are marked in both fl oz and mL. According to the American Academy of Pediatrics, newborns typically consume 1-3 fl oz (30-90 mL) per feeding, increasing to 6-8 fl oz (177-237 mL) by six months.

Comparing drink sizes internationally: A US "tall" coffee at Starbucks is 12 fl oz (355 mL). In many European countries, a standard coffee is 150-200 mL (5.1-6.8 fl oz). A US pint of beer is 16 fl oz (473 mL), while a UK pint is 20 Imperial fl oz (568 mL) -- the UK pint is actually 20% larger. Our mL to Fluid Ounces Converter handles the reverse calculation.

Tips for Accurate Volume Conversions

• For cooking, multiply by 30 as a quick estimate: 1 fl oz is approximately 30 mL (exact: 29.57 mL). This 1.4% overestimate is acceptable for most recipes. For precise baking, use the exact factor.
• Check whether recipes use US or UK fluid ounces: British recipes from the UK use Imperial fluid ounces (28.41 mL each), which are 4.1% smaller than US fluid ounces. A British recipe calling for 10 fl oz of milk means 284 mL, not 296 mL.
• Remember common benchmarks: 8 fl oz = 1 cup = 237 mL. 500 mL water bottle = 16.9 fl oz. 750 mL wine bottle = 25.4 fl oz. These help with quick mental estimates.
• Use a liquid measuring cup for accuracy: Dry measuring cups are designed to be filled to the brim and leveled, while liquid measuring cups have a spout and measuring lines. Using the wrong type can introduce 10-15% measurement errors.
• For medication, always use mL: The FDA recommends using milliliter-marked dosing devices for liquid medications. Kitchen spoons vary in size by up to 25%. Our Tablespoon to Teaspoon Converter covers cooking spoon conversions, but for medication always use a marked dosing syringe.

US vs UK vs Metric Volume Comparison

Volume measurement systems differ significantly between the US, UK, and metric countries. The table below highlights key differences that can cause confusion when following international recipes or comparing product sizes.