One fluid ounce equals how many ounces?

Answer 1

If you are measuring water, one fluid ounce of water equals one ounce in weight. However, this conversion only applies to water, since all other ingredients have different densities, which have to be taken into account when converting them from a measure of volume such as "fluid ounces" or "mils", or "cups" ( all "how much can I fit in this space?" measures), to a measure of weight such as "ounces", "grams".

For example, imagine a cup that fits exactly one fluid ounce. If you were to measure a cup of flour, and then weigh it, and then measure a cup of beaten egg white, then weigh it, you would find that the same "volume" of these to items would have very different weights. This is why converting ingredients other than water from fluid ounces to weight ounces is not straight forward.

Even milk is only 98% water and 2% milk solids, which means that a conversion, to be accurate, would not be 1:1 (fluid ounces:weight ounces). (Although, having said that, a 1:1 conversion for a volume of milk to a weight of milk would only be marginally inaccurate, so the conversion is fine for home-cooking purposes. And to be fair, most weighing scales are not completely accurate, and measuring liquids in a measuring jug is not very accurate either, so a marginally inaccurate conversion is really not a major issue.)

Answer 2

One fluid ounce is equivalent to 0.125 ounces when using the avoirdupois system of measurement.