US Gallons to US Fluid Ounces (gal to fl oz)
1 US gallon equals 128 US fluid ounces exactly.
How to convert US gallons to US fluid ounces
To convert US gallons to US fluid ounces, multiply the number of US gallons by 128. This factor is exact. To go the other way, multiply US fluid ounces by 0.0078125.
US fluid ounces = US gallons × 128
Example: 10 US gallons = 1,280 US fluid ounces.
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 Gallon (gal)
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
US Fluid Ounce (fl oz)
One 128th of a US gallon, 29.5735 mL. Not the same as the weight ounce, and about 4% larger than the imperial fluid ounce.
Fluid ounce began as an attempt to link volume to weight: the volume occupied by one ounce of some substance, such as wine in England or water in Scotland. Definitions varied by region and by liquid. When Britain defined its imperial gallon in 1824 as the space of ten pounds of water, the imperial fluid ounce came out so that an ounce of water weighs about one avoirdupois ounce. The US fluid ounce followed a different path and comes from the older wine gallon.
The US fluid ounce is exactly 1/128 of a US gallon, 29.5735295625 milliliters, about 4 percent bigger than the imperial one at 28.4130625 milliliters. American nutrition labels use yet another figure, treating one fluid ounce as 30 milliliters, a convenient rounding for serving sizes. The name is a trap, because a fluid ounce measures space while a weight ounce measures mass. A US fluid ounce of water weighs a bit more than an ounce of weight, while a fluid ounce of honey weighs considerably more.
1 US fluid ounce = 0.02957352956 liters (approximately).
Sources: Wikipedia: Fluid ounce; NIST SP 811, Appendix B.8: conversion factors for volume; 21 CFR 101.9: nutrition labeling household measures
Related conversions
- US fluid ounces to US gallons (reverse)
- US gallons to liters
- US gallons to milliliters
- US gallons to US cups
- US gallons to cubic meters
- US gallons to cubic centimeters
- US gallons to US quarts
- US gallons to US pints
- US gallons to US tablespoons
- US gallons to US teaspoons
- US gallons to metric cups
- US gallons to metric tablespoons
- US gallons to metric teaspoons
- Liters to US fluid ounces
- Milliliters to US fluid ounces
- US cups to US fluid ounces
- Cubic meters to US fluid ounces
- Cubic centimeters to US fluid ounces
- US quarts to US fluid ounces
- US pints to US fluid ounces
- US tablespoons to US fluid ounces
- US teaspoons to US fluid ounces
- Metric cups to US fluid ounces
- Metric tablespoons to US fluid ounces
- Metric teaspoons to US fluid ounces
See all volume units.