Gallon (UK) (gal) - Unit Information & Conversion

Definition

The UK gallon (Imperial gallon) is a unit of volume defined as 4.54609 litres.

History

The Imperial gallon was defined based on the volume of 10 pounds of distilled water weighed in air with brass weights with the barometer standing at 30 inches of mercury and at a temperature of 62 °F.

Common Uses

• Fuel Measurement: Used for measuring fuel (petrol, diesel) in the UK and some Commonwealth countries.
• Beverages: Selling milk and other beverages in large containers in the UK.
• Household Liquids: Measuring paint and other household liquids.
• Pools & Water: Pool capacity and water usage measurements in the UK.
• Industry: Some industrial applications in countries using the Imperial system.

The Imperial Gallon: A Legacy of Maritime Power

The Imperial Gallon, established by the Weights and Measures Act of 1824, was defined as the volume of 10 pounds of distilled water at ^{\circ}\text{F}$ weighed in air. This definition resulted in a volume of approximately .54609\text{ liters}$. While the United States continued using the older Queen Anne's Wine Gallon (approx .785\text{ liters}$), the Imperial system became the standard for the vast British Empire, facilitating global trade and navigation for over a century.

Even today, after official metrication in the UK and much of the Commonwealth, the Imperial gallon persists in certain sectors, most notably in the reporting of fuel economy for internal combustion engine vehicles.

Fuel Economy: Why the UK 'MPG' is Different from the USA

One of the most common sources of confusion for international travelers and automotive enthusiasts is the difference between UK and US Miles per Gallon (MPG). Because the Imperial gallon is approximately 20% larger than the US gallon, a vehicle rated at \text{ MPG}$ in a British car magazine is actually achieving only about .6\text{ MPG}$ in US terms.

This historical divergence makes direct comparisons difficult without careful conversion. For companies operating global logistics fleets, understanding this distinction is vital for accurate budgeting and environmental reporting across different territories.

The Global Imperial Volume Registry: 200 Benchmarks

1. Log 401: The capacity of a standard vintage British fuel jerrycan (.5\text{ gal}$).
2. Log 402: The volume of a traditional English cider barrel.
3. Log 403: The amount of water in a standard British domestic cistern.
4. Log 404: The capacity of an early 20th-century Rover fuel tank.
5. Log 405: The volume of an Imperial pint (1/8th of a gallon).
6. Log 406: The capacity of a classic London Routemaster bus fuel tank.
7. Log 407: The amount of fuel in a vintage Spitfire's primary tanks.
8. Log 408: The volume of a standard English beer cask (Firkin).
9. Log 409: The capacity of a residential water heater in a Victorian terrace.
10. Log 410: The volume of rain collected in a standard British rain butt.
11. Gal UK 411: One.
12. Gal UK 412: Two.
13. Gal UK 413: Three.
14. Gal UK 414: Four.
15. Gal UK 415: Five.
16. Gal UK 416: Six.
17. Gal UK 417: Seven.
18. Gal UK 418: Eight.
19. Gal UK 419: Nine.
20. Gal UK 20: Ten.