What is a pint of beer in the UK measured as, in milliliters?

In the United Kingdom, a standard pint of beer is precisely defined as 568.261 milliliters. This measurement stems from the British Imperial system, which standardized various units of volume in the 19th century. While many countries have adopted the metric system for most measurements, the pint remains a legally recognized and commonly used unit for serving draught beer and cider, as well as for milk in returnable containers across the UK and Ireland.

The Imperial pint's origins can be traced back to the Weights and Measures Act of 1824, which established the Imperial gallon as the volume of ten pounds of distilled water at a specific temperature. Since a pint is traditionally one-eighth of a gallon, this act solidified the volume of the Imperial pint that is still in use today. Before this standardization, various "gallons" existed, leading to inconsistencies in measurements across different regions and for different commodities like wine or ale.

A common point of confusion arises when comparing the UK pint to its American counterpart. The US liquid pint is considerably smaller, measuring approximately 473 milliliters. This difference exists because the United States adopted a different definition for its gallon, based on the British wine gallon from 1707, which was 231 cubic inches. In contrast, the Imperial gallon, from which the UK pint is derived, is larger. Consequently, the British Imperial pint is about 20% larger than the US liquid pint. This distinction highlights how historical legislative decisions continue to influence everyday measurements in different parts of the world.