There are 13.525 fluid ounces in 400 milliliters. Using a unit conversion calculator is the easiest method for finding this answer. Unit conversion calculators allow the user to select two units and enter any number of either unit to convert to the other.
Fluid ounces are a measurement used in the United States. One milliliter is just over 3 percent of an ounce. Liters and milliliters are used in countries that use the International Standard of Measurement (SI). Milliliters are not themselves an SI unit, but because they are equivalent to 1 cubic centimeter, they are widely accepted in SI countries.