US Cups to Imperial Gallons (cup to gal (UK))

1 US cup equals 0.05204213654 imperial gallons (rounded).

1 US cup = 0.05204213654 imperial gallons

How to convert US cups to imperial gallons

To convert US cups to imperial gallons, multiply the number of US cups by 0.05204213654. The factor is rounded to 10 significant digits. To go the other way, multiply imperial gallons by 19.21519881 (rounded).

imperial gallons = US cups × 0.05204213654

Example: 10 US cups = 0.5204213654 imperial gallons.

Pints, quarts, gallons and fluid ounces differ between the US and the UK. Units are labeled 'US' or 'imperial' to avoid confusion.

About these units

US Cup (cup)

US customaryCurrent unit

One sixteenth of a US gallon, 236.588 mL (8 US fluid ounces). The standard US recipe cup.

Cups began as household drinking vessels, not scientific units, which is why they remain the messiest measures in the kitchen. The US customary cup was defined by slicing up the gallon: half a pint, or eight US fluid ounces, about 236.6 milliliters. Unlike the larger units, nobody ever fixed it to a physical vessel, so it exists only as a fraction of the gallon.

The customary cup is not the only American cup. For nutrition labels, US regulation defines a cup as exactly 240 milliliters, a rounder figure that sits slightly above the customary size. Packaged foods therefore list a serving in the legal cup while a measuring cup from the hardware store follows the customary definition. The gap is 3.4 milliliters, which hardly matters for soup but can matter in baking. Cup measures also hide the weight of dry ingredients, since a cup of sifted flour and a cup of packed flour differ substantially, which is why much of the world prefers grams.

1 US cup = 0.2365882365 liters (exactly).

Sources: Wikipedia: Cup (unit); NIST SP 811, Appendix B.8: conversion factors for volume; 21 CFR 101.9: nutrition labeling household measures

Imperial Gallon (gal (UK))

Imperial (British)Current unit

Exactly 4.54609 liters, the volume of 10 pounds of water. Used for fuel economy in the UK (miles per gallon) and historically across the Commonwealth.

Britain unified its confusing gallons by act of Parliament in 1824. Before then, the country used separate ones for wine at 231 cubic inches, ale at 282 and corn at about 268.8. The 1824 reform replaced them with the imperial gallon, defined as the volume of ten pounds of distilled water, calculated at 277.274 cubic inches. A new definition in 1889 slightly changed that, and after the liter was restored to exactly a cubic decimeter in 1964, Canada and then the UK in 1976 adopted the exact value of 4.54609 liters.

Because the United States kept the 231-cubic-inch wine gallon, an imperial gallon is about 20 percent larger than a US gallon. That explains why a car rated at 40 miles per gallon in Britain is less impressive in American terms, since it comes to roughly 33 US miles per gallon. Ireland dropped the gallon as a primary trade unit at the end of 1993 and the UK at the end of September 1995, but it lives on in British fuel-economy figures and older recipes.

1 imperial gallon = 4.54609 liters (exactly).

Sources: Wikipedia: Gallon; UK Weights and Measures Act 1985, Schedule 1

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