UK Fluid Ounces
Abbreviation/Symbol:
fl oz
Unit of:
Worldwide use:
UK fluid ounces are a unit of volume commonly used in the United Kingdom and some other countries that were once part of the British Empire.
Definition:
The UK fluid ounce is slightly different from the US fluid ounce, with 1 UK fluid ounce being equivalent to approximately 28.41 milliliters. This discrepancy arises from the historical development of the fluid ounce measurement in the UK, which is based on the imperial system of units.
Origin:
The UK fluid ounce is 28.4131 milliliters, close to the volume of one ounce of water. That is by design: the imperial gallon is the volume of 10 pounds of water, and a fluid ounce is 1/160 of it.
The Weights and Measures Act of 1824 established this ounce, and other Commonwealth countries adopted it. The US did not: its fluid ounce is 29.5735 milliliters, about 4% bigger.
Usage context:
A UK fluid ounce is 28.41 milliliters, a 160th of an imperial gallon, which makes it about 4% smaller than the US fluid ounce (29.57 milliliters). The UK pint has 20 of them against the US 16, so it ends up the bigger pint.