Both use cups and ounces to measure ingredients—but they don’t always mean the same thing.
Here’s a common cooking question—how many ounces in a cup? Unfortunately, the answer isn’t as simple as it seems. Though they both have the same name, there's a difference between ounces, which measure weight, and fluid ounces, which measure volume.
Measuring in Ounces
Liquid measuring cups indicate that 1 cup = 8 ounces. But what they really mean is 1 cup of liquid = 8 fluid ounces. For dry measurements, the rules change. Because dry ingredients vary greatly in weight, you can’t rely on the same conversion. For example, 1 cup of all-purpose flour weighs 4.5 ounces, not 8 ounces. On the other hand, 1 cup of chocolate chips weighs a little over 6 ounces.
So what do you do? If a recipe calls for an ounce amount of a dry ingredient, the best option is to weigh that ingredient with a scale. If a recipe calls for an ounce amount of a liquid, you can measure it in a liquid measuring cup.
Measuring in Cups
There are two main types of measuring cups—dry measuring cups and liquid measuring cups—and it matters which one you use. Dry measuring cups are designed to measure dry ingredients like flour, nuts, and berries, while liquid measuring cups are designed to measure liquids like water, cooking oil, and yogurt.
Liquid measuring cups are usually glass or plastic with a handle. They allow you to pour a liquid into the cup and bring it even with a measurement line without spilling. Dry measuring cups, on the other hand, hold the exact amount of an ingredient and should be leveled off with a flat edge.
Using the right type of measuring cup can determine the outcome of the recipe you’re making. In baking, making improper measurements can completely throw off a recipe. For example, when measuring flour, a dry measuring cup lets you portion out the exact amount that you need.
Lightly spoon the flour into a dry measuring cup, then level it by taking a flat edge and pushing it across the top of the cup to remove the excess. Doing so with a liquid measuring cup could result in tapping or packing the flour down, causing you to add more than the recipe needs.
Likewise, it’s tough to fit the exact amount of a liquid in a dry measuring cup without spilling it over the sides. For example, for chicken stock, a liquid measuring cup lets you pour in a precise amount without splashing it all over your kitchen counter.
Here’s a good rule of thumb to follow—when measuring dry ingredients, use dry measuring cups or weigh them with a scale. For liquids, stick to a liquid measuring cup.