A cup (C) is a unit of volume primarily used in the U.S. customary and imperial systems of measurement. A cup also has a number of other definitions, but the focus of this site will be the cup as measured in the US customary and imperial systems of measurement.

In the US customary system, 1 cup is equal to exactly 236.5882365 milliliters (mL). In the UK, the cup is based on imperial fluid ounces, and is equal to 284.131 mL.

The US also has another definition of a cup, called the US legal cup, which is equal to 240 mL. The US legal cup is used mainly for labeling based on US laws, while the US customary cup (referred to as just cup), is used largely for cooking measurements. The figure below is an example of a set of measurement cups.

Below is a list of equivalences between the US customary cup, other cup measurements, and other measurements of volume:

1 cup  ≈  0.986 US legal cups
   ≈  0.833 imperial cups
   =  gallons
   =  quarts
   =  pints
   =  8 fluid ounces
   =  16 tablespoons
   =  48 teaspoons