Short answers, pulled from the story.
The wine gallon was legally adopted in the United States in 1836. This standard was defined as 231 cubic inches and historically linked to the weight of eight medieval merchants pounds of wine. The specific volume formed a cylinder six inches deep and seven inches in diameter.
The imperial gallon is approximately 20 percent larger than the US gallon. Britain adopted the imperial gallon in 1824 as the volume of 10 pounds of distilled water, while the US gallon remained 231 cubic inches. This divergence means an imperial fluid ounce is 20 percent larger than a US fluid ounce.
The imperial gallon remains the standard for petrol in four British Overseas Territories and four Caribbean nations. These jurisdictions include Anguilla, the Cayman Islands, Antigua and Barbuda, and Saint Lucia. These eight locations share a unique cultural quirk of driving on the left side of the road while measuring fuel in gallons.
The Dubai Electricity and Water Authority transitioned its water billing from imperial gallons to cubic metres in March 2025. This change followed similar moves by the United Arab Emirates in 2010 and Guyana in 2013. The European Union removed the gallon from its list of primary units of measure in 1994.
The US dry gallon was defined as one-eighth of a US Winchester bushel and equal to approximately 268.8 cubic inches. This measure was used for grain and other dry commodities until the 1990s. It was replaced by the peck and the bushel in modern trade and is no longer included in relevant statutes.
The standard bottle size for liquor in the United States was historically known as the fifth, which is one-fifth of a US gallon. This volume is approximately 757 milliliters and was slightly larger than a reputed quart. Although spirit sales in the US were officially switched to metric measures in 1976, the 750 milliliter bottle is still commonly referred to as a fifth by consumers and retailers.