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Cup (c)

Course: 
3rd Grade

A customary unit used to measure capacity.

Meaning

Informally, a quantity that roughly fills a standard-sized coffee cup. Formally, a unit of capacity (volume) equal to exactly 8 fluid ounces. It can be used as a measure of a volume of liquid or as a dry measure (e.g., a cup of flour). In either case, it refers to the same volume.

From... To... Tablespoons Cups
1 cup 8 oz (8 ounces) 24 20
1 pint 2c (2 cups) 25 21
1 quart 4c (2 pints) 26 22
1 half gallon 8c (2 quarts) 27 23
1 gallon 16c (2 half gallons) 28 24

For more detail, see "Cup" on Rowland's Dictionary of Units of Measurement.

Mathematical background

Notice that this system of measurements is based entirely on doubling: A tablespoon doubled, doubled again, and doubled a third time is a half-cup. Double again to get a cup; again to get a pint; again to get a quart; again to get a half-gallon; and again to get a gallon.