An ounce is an ounce is an ounce, right?
Well, yes . . . kind of. But are you talking about a fluid ounce or a weight ounce? This is where it gets confusing.
Fluid Ounces Versus Net Weight Ounces
Fluid ounces (fl oz) measures the volume of a liquid, or how much room this liquid takes up. Net weight (Net Wt) measures the mass of a solid, or how much the product weighs.
Since fluid ounces and net weight measure different things, they don’t equal each other. For example, 8 fl oz of juice doesn’t equal Net Wt 8 oz of chips. It’s easy to determine which measurement to use for most products, but what about something that is viscous and lands between a liquid and a solid, such as honey?
According to the Food and Drug Administration’s (FDA) label regulations on the net quantity of contents: if a food is solid, semisolid, or viscous, it should be expressed in terms of weight. If the food is a liquid, it should be expressed in a fluid measure (e.g. fl oz). And for non-food products such as lotions or dish detergents, fluid ounces should be listed on the label.
There’s another piece to this puzzle. Manufacturers buy empty packaging containers named by what they might hold. A large grease cartridge is sold as a 14 oz cartridge. Manufactured products, however, may be sold by the actual weight of the finished product. Dense products often times weigh in as more than what the container was predicted to hold.
There is another kind of weight: gross weight. Gross weight combines the weight of the container with the weight of the product. It is not something most purchasers see as it is generally used only to calculate shipping costs.
