What is the difference between a quantity and a unit? If you are working science or math problems, the answer to this question is the quantity is the amount or numerical value, while the unit is the measurement. For example, if a sample contains 453 grams, the quantity is 453 while the unit is grams. For this example, the quantity is always a number, while units are any measure, such as grams, liters, degrees, lumens, etc. In a recipe, the quantity is how much you need and the unit describes what you use to measure it. For example, 3 tablespoons and 3 teaspoons have the same quantity, but they use different units. It's important to note the units, whether it's in the lab or in the kitchen!

### Units in Science Versus Math

There are, however, other ways to answer the question. A quantity may also be considered to be a nonspecific number of items, particularly ones that would be hard to count. You could refer to a "quantity of water" or a "quantity of air" and not cite the number of molecules or mass.

Units sometimes refer to individual sets. For example, if you are studying chemistry, you might have a unit on gases, a unit on conversions, and a unit on balancing equations. A set of rooms in an apartment building may be called a unit. Any removable component in a piece of electronics might e called a unit. If the term unit is used this way, quantity can mean how many units you have. If you need 3 units of blood for a transfusion, the number 3 is the quantity. Each unit is a single container of blood.