Imperial Fluid Ounces to US Gallons (fl oz (UK) to gal)

1 imperial fluid ounce equals 0.007505937034 US gallons (rounded).

1 imperial fluid ounce = 0.007505937034 US gallons

How to convert imperial fluid ounces to US gallons

To convert imperial fluid ounces to US gallons, multiply the number of imperial fluid ounces by 0.007505937034. The factor is rounded to 10 significant digits. To go the other way, multiply US gallons by 133.2278695 (rounded).

US gallons = imperial fluid ounces × 0.007505937034

Example: 10 imperial fluid ounces = 0.07505937034 US 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

Imperial Fluid Ounce (fl oz (UK))

Imperial (British)Current unit

Exactly 28.4130625 mL. About 4% smaller than the US fluid ounce.

Imperial fluid ounce comes from the 1824 reform that defined the British gallon as the volume of ten pounds of water. Because a gallon was set at 160 fluid ounces, an ounce of water weighs about one ounce of mass, around 28.35 grams. That neat link between volume and weight was the point of the imperial scheme, and it explains why people long thought of fluid ounces and weight ounces as nearly the same.

Today an imperial fluid ounce is exactly 28.4130625 milliliters, one twentieth of an imperial pint. That is about 4 percent smaller than the US fluid ounce at 29.57 mL, so a US recipe using fluid ounces does not map one-for-one onto a British one. UK trade rules restricted its use in 1995, and it lives on mostly on older labels, in bars and in recipes. Twenty of them fill an imperial pint, which makes the pint the easiest way to picture one.

1 imperial fluid ounce = 0.0284130625 liters (exactly).

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

US Gallon (gal)

US customaryCurrent unit

Exactly 231 cubic inches or 3.785411784 liters (128 US fluid ounces). About 17% smaller than the imperial gallon.

The US gallon is a survivor of English wine trade. Around 1706, a statute in Queen Anne's reign fixed the wine gallon at exactly 231 cubic inches, settling confusion among the competing gallons for wine, ale and corn. British colonies in North America used that wine gallon, and in 1824 Britain replaced all its gallons with a new imperial one while the United States kept the old measure. It was adopted as the legal US standard in 1836 and is still defined as exactly 231 cubic inches, or 3.785411784 liters.

That makes the US gallon about 17 percent smaller than the imperial gallon, a difference that explains why American and British fuel-economy figures cannot be compared directly. Everyday uses are milk jugs, paint cans and gasoline pumps. One gallon divides evenly into four quarts, eight pints, sixteen cups and 128 fluid ounces. A gallon of water weighs a little over 8 pounds, an easy figure to remember when loading a car with water jugs.

1 US gallon = 3.785411784 liters (exactly).

Sources: Wikipedia: Gallon; NIST SP 811, Appendix B.8: conversion factors for volume

Related conversions

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