Fluid Ounce to Milliliter Conversion – fl oz to mL Example Problem

Fluid ounces to milliliter conversion example
fl oz to mL conversion. How many milliliters are in a water bottle?
Credit: Photo by Steve Johnson on Unsplash

Volume measurements can be some of the most confusing set of measurements. This example problem shows how to convert fluid ounces to milliliters. This conversion is also useful for converting recipes from European and Asian sources to the commonly used measurements in American kitchens.

The fluid ounce (fl oz) in the US is derived from the US gallon (gal) measurement. The US gallon is currently defined as the volume enclosed by 231 cubic inches and a fluid ounce is 1/128 of a US gallon. A milliliter is 1/1000 of a liter. The conversion between a US gallon and a liter is:

1 US gallon = 3.758 liters

Once all these factors are taken into effect, the conversion between the fluid ounce and the milliliter is:

1 fl oz = 29.5735 mL

Fluid ounce to Milliliter Conversion Example Problem

Question: Most beverages in the US come in 12, 16, or 20 fl oz containers. Water bottles are different by coming in 16.9 fl oz containers. How many milliliters of water comes in these containers?


16.9 fl oz = x mL

Use the conversion factor from above. Set up your conversion factor so the desired unit (mL) is on top.

fluid ounce to milliliter - fl oz to mL conversion step 1

Setting the desired unit on top allows you to cancel out the undesired unit.

16.9 ⋅ 29.5735 mL = x mL

499.79 mL = x mL

Answer: There are 499.79 mL in 16.9 fl oz.

This is basically 500 mL or a half liter.

For many Americans, a liter is an abstract measurement and not something overly familiar. Gallons are gas can or milk jug sized. Now you have an idea of the size of a liter: 2 water bottles.