Fluid Ounces to Milliliters Calculator

Background.

A fluid-ounces-to-milliliters calculator translates US recipe measures, beverage labels, and container capacities into metric volume. A four-fluid-ounce bottle is exactly 118.29411825 mL under the US liquid-gallon definition, although packaging may show a rounded nominal amount.

This calculator uses the exact US fluid ounce: 1/128 of a US gallon, with the gallon defined as exactly 3.785411784 liters. Dividing that exact value by 128 gives exactly 29.5735295625 milliliters per US fluid ounce. The factor is not interchangeable with the imperial fluid ounce used in some UK contexts, which has a different definition.

This page is a unit converter, not a medication dosing tool. Do not derive or round a medicine dose from a container-size conversion. For any medication, follow the product label and use the supplied dosing device, pharmacist, or clinician. The mathematics here can express a stated volume in another unit, but it cannot decide what amount is safe or prescribed.

What is fluid ounces to milliliters calculator?

A US fluid ounce is a volume equal to 1/128 of a US liquid gallon. A milliliter is 1/1000 of a liter. The exact relation is 1 US fl oz = 29.5735295625 mL, derived from the exact 3.785411784-liter US gallon. The imperial fluid ounce is different, so confirm the source system before converting.

How to use this calculator.

1. 01Enter the volume in US fluid ounces - for example, a recipe measurement, beverage label, or container size.
2. 02Read the converted value in milliliters, shown to full precision.
3. 03Check the liters field if you are working with a larger container, such as a multi-dose bottle or a bulk liquid.
4. 04For medication, use the label and supplied dosing device; do not use this general converter to choose or round a dose.

The formula.

The conversion is purely multiplicative because volume has no offset - zero fluid ounces is zero milliliters. The US fluid ounce is defined as exactly 1/128 of a US liquid gallon; since the US gallon is exactly 3.785411784 liters (NIST Special Publication 811), dividing by 128 gives 29.5735295625 milliliters per fluid ounce, with no rounding anywhere in the derivation. In the worked example, a 4 fl oz bottle multiplied by 29.5735295625 gives 118.29411825 mL. For a 12 fl oz can, the same factor gives 354.88235475 mL. All arithmetic runs through Decimal.js at full precision, so a syringe marked in tenths of a milliliter, or a lab pipette marked in hundredths, gets a number that matches the definition exactly rather than one that has drifted from repeated floating-point rounding.

A worked example.

Frequently asked questions.

References& sources.

1. [1]National Institute of Standards and Technology. NIST Special Publication 811, 2008 Edition - Guide for the Use of the International System of Units (SI), Appendix B. Source for the US gallon (3.785411784 L) from which the exact US fluid ounce factor is derived.
2. [2]National Institute of Standards and Technology. NIST Handbook 44, Appendix C - General Tables of Units of Measurement. US legal-metrology reference for the fluid ounce and other US customary volume units.