Relationship Between Fluid Ounces and Gallons

The conversion between US fluid ounces and US gallons is based on the relationship where 1 US gallon equals exactly 128 US fluid ounces.

1 gal = 128 fl oz

Therefore,

1 fl oz = 1/128 gal = 0.0078125 gal

To convert fluid ounces to gallons, we divide the value in fluid ounces by 128, or multiply by 0.0078125.

For example, 128 fluid ounces equal 1 gallon, and 256 fluid ounces equal 2 gallons.

Fluid Ounce

What is a Fluid Ounce (fl oz)?

A fluid ounce (symbol: fl oz) is a unit of volume measurement for liquids in the US customary system. One US fluid ounce equals approximately 29.5735 milliliters or 0.0295735 liters. It is commonly used for measuring smaller quantities of beverages, cooking ingredients, and medications.

Origin and Etymology

The fluid ounce originated from the Roman 'uncia,' meaning one-twelfth. Historically, one fluid ounce was defined as the volume occupied by one ounce (weight) of water. While the weight-based definition is no longer used, the term 'fluid ounce' distinguishes it from the ounce used for measuring weight (the avoirdupois ounce).

Current Use and Applications

Fluid ounces are widely used in the United States for measuring beverages, particularly in restaurants, bars, and on nutrition labels. Soft drinks are often sold in 12 fl oz cans or 20 fl oz bottles. Recipes frequently call for ingredients measured in fluid ounces, and medication dosages are often specified in fluid ounces. The unit is also common in the beauty and personal care industry for measuring lotions, shampoos, and perfumes.

US vs Imperial Fluid Ounce

Similar to gallons, there is a difference between US and imperial fluid ounces. The US fluid ounce (29.5735 mL) is slightly larger than the imperial fluid ounce (28.4131 mL) used in the UK. This converter uses the US fluid ounce standard.

Gallon

What is a Gallon (gal)?

A gallon is a unit of volume measurement used primarily in the United States for measuring liquids. The US liquid gallon equals exactly 128 US fluid ounces, 4 quarts, or approximately 3.785 liters. It is commonly used for measuring fuel, milk, water, and other beverages.

History and Origin of the Gallon

The gallon has its origins in medieval England, where it was used to measure wine and beer. Over time, different types of gallons emerged, including the wine gallon, ale gallon, and imperial gallon. The US gallon is based on the old English wine gallon (Queen Anne's gallon) which was standardized in 1707. Today, the US liquid gallon is defined as exactly 231 cubic inches.

Modern Applications of Gallons

In the United States, gallons are the standard unit for measuring liquid volumes in everyday life, particularly for gasoline, milk, bottled water, and other beverages. Gas stations display fuel prices per gallon, and grocery stores sell milk and juice by the gallon. The gallon is also used in industrial applications, agriculture (for pesticides and fertilizers), and swimming pool maintenance.

Different Gallon Standards

It's important to note that the US gallon (3.785 L) differs from the imperial gallon (4.546 L) used in the United Kingdom and some Commonwealth countries. The imperial gallon is approximately 20% larger than the US gallon. This converter uses the US liquid gallon standard.

Fluid Ounce to Gallon Conversion Table

The conversion of fluid ounces to gallons for certain values are provided below: