Originally Posted by jasonr
Is a fl oz a volume or mass measurement?
Strictly speaking a fluid oz is a measure of volume
Fortunately one fluid oz water (measured by either the US or British Imperial system) is basically equal to one oz by weight.
Liquids with a similar density to water, such as milk, also conform to the conversion that 1 fluid oz (volume) = 1 oz (weight).
If, however, you're measuring a heavier liquid (such as honey), this "equality" doesn''t hold.