When it comes to labeling your product, a few missing adjectives and precious little space for typography can add up to some pretty hefty confusion. That's why we wants you to be on first name terms with some common, easily understood terms of measurement and understand why it's vital to include them on your packaging.
Let's use a container of milk and a box of pancake mix as our example.
Liquids and solids you say. Right!
Now take it one step further and think in terms of Volume (the milk) and Weight (the pancake mix).
Why? Because a gallon of milk -- like any liquid -- is measured by volume ("fluid ounces"). And a box of pancake mix is sold by weight (weight ounces).
Here's an easy way to remember:
Fluid Ounces: Liquid.
Weight Ounces: All that other stuff! (Technically, it goes something like this: Use Fluid measure units if the item is liquid. Use Weight measure units if the item is solid, semisolid or viscous, or a mixture of solid and liquid.)
And even though they both use the word "ounces" there is no direct, straight line conversion between the two. They are simply not the same thing. To convert Fluid Ounces of a liquid to a Weight measurement (ounces, pounds, etc.), you must know the density of the liquid product, which is commonly expressed in terms of X weight units/volume units.
See for yourself! 8 fluid ounces of whole milk weighs in at just about 8.6 ounces. Whole milk has -- on average -- a density of 1.075 ounces per one fluid ounce. 8 * 1.075 = 8.6
When it comes to volume, 8 fluid ounces always takes up the same space. Always!
Just like our milk weight conversion example above, it's important to remember that 8 fluid ounces can weigh a ja-zillion different weights depending on what fluid we are talking about.
For example: 8 fluid ounces of liquid mercury weighs in at 7.06 pounds. It's the densest liquid known at room temperature. That means it has a density of 14.08 ounces per one fluid ounce. 8 * 14.08 = 112.64 ounces or 7.04 pounds.
Now that you're a measuring expert, let's work together to take it to an even more useful level of specificity. When it comes to expressing weight, you need to understand the difference between Gross Weight and Net Weight.
Let's use pancake mix as an example. If the box reads "12 ounces" is the weight of the product in the box, or the weight of the product PLUS the weight of the box? "12 Ounces" is simply not as clear as it could be. It's either "Gross Weight 12 Ounces" (the combined weight of the mix PLUS the box) or "Net Weight 12 Ounces" (the weight of the mix only).
There are times when it's vitally important to know both measurements about your product. Gross weight is a key factor when it comes to calculating shipping, transit and all that other fun stuff that accompanies bringing goods to market.
So remember, the amount of Liquid is always expressed in Fluid Ounces. Everything else... is basically not!