Do you know how many ounces in a cup? The term ounces (also known as fluid ounces, fluid ounces, or ounces per fluid ounce) is the measure of the amount of a liquid or solid in a unit of measure, the standard imperial gallon, cubic foot, or another unit. Depending on the use, a unit might be known as fluid ounce, fluid ounce cup, or fluid ounce Cuvee. Most types of units of measurement are defined with reference to a fluid unit, such as the ounce. For example, a unit of dry measure (volume) such as the gallon is defined as being the volume of water that contains one ounce of dissolved solids.

Compared with other units of measure such as stone (such as a standard cubic centimeter, which is 0.000451 US quart, or 0.00437 cubic centimeters), as well as the analogous system of the area and volume measurement, the ounce is widely used in science and industry. This is because the measurement is consistent across the whole of science, whereas the other units are often defined with reference to another unit. The system of units used for laboratory science is known as the SI.

One ounce (or a standard fluid ounce) of liquid water is the standard unit for water-related measurements. It is equal to exactly 3.989976 UK/ imperial quarts, just over 33.5 liters, just under 548 US pints, and about 97.053 US fl oz.

In everyday use

A standard fluid ounce of any liquid can be expressed as follows. Note that small differences are common, and usually depend on the fluid.

1 fluid ounce = 3.989976 litres = 868.8 milliliters = 10,904.75 milliliters = 33.508 litres = 1 fluid ounce

ISO, the international standard body for measurement standards, defines the following standards:

US customary units ​ 1⁄ 8 ounce, or US fluid ounce

“One fluid ounce of fluid is equal to exactly 3.989976 liters. One fluid ounce of fluid is equal to exactly 10.904.75 liters. One fluid ounce of fluid is equal to exactly 97.053 liters. One fluid ounce of fluid is equal to exactly 43.543 liters.”

In chemistry, it is customary to write out fluid ounces instead of fluid milliliters. The first milliliter, 0.0709 fluid milliliter, is exactly equal to 1 fluid ounce.

Millilitres of water in glass

In Europe and the United States, a fluid ounce is sometimes used as the name of units of measure in home heating oil, to replace US customary gallons. In the US, heating oil is usually sold by gallons.

The cubic centimeter is usually specified by the cubic meter (1.005 cu ft or 1,100 mL), though some heating oil suppliers specify cubic centimeters (1.00046 cu in or approximately 46.36 mL) to avoid confusion with the imperial system.

In the United States, fluid ounces are generally used when talking about volume measurements of liquids, as opposed to (compressed) gas volume measures.

Not to be confused with fluid ounce of water

In an earlier version of the system, fluid ounces per cubic foot were used as the units of fluid volume. However, because of the significant differences in physical size of liquids, such as those between molasses and gasoline, it was easier to denote the fluid ounce per cubic foot in the imperial system, than it would have been in the customary system,