A fluid ounce is a unit of measurement for liquids, abbreviated fl oz. When you see a label on a can of soda that says “12 fl oz,” it's telling you the volume of liquid inside. In the United States, one fluid ounce equals about two tablespoons, and there are eight fluid ounces in a cup.

Despite its name, a fluid ounce doesn't measure weight the way a regular ounce does. A regular ounce measures how heavy something is, while a fluid ounce measures how much space a liquid takes up. This distinction matters because different liquids weigh different amounts even when they take up the same space: eight fluid ounces of honey weighs more than eight fluid ounces of water, even though both fill the same measuring cup.

Most countries use milliliters instead of fluid ounces, but in the United States, you'll see fluid ounces everywhere: on juice boxes, milk cartons, shampoo bottles, and medicine labels. When a recipe calls for 6 fl oz of milk, you can measure it using a liquid measuring cup marked with fluid ounce lines. Understanding fluid ounces helps you follow recipes, compare product sizes at the store, and know exactly how much you're drinking.