What is US gallon?
A US gallon is a volume unit equal to 128 US fluid ounces, or approximately 3.785 litres. It is the standard unit for fuel, milk, and other liquid products in the United States.
Real-world uses
US gallons are used for fuel pricing and vehicle fuel economy (miles per gallon) in the United States. Milk, water, and paint are commonly sold in gallon containers. Pool volumes and water heater capacities are specified in gallons.
History
The US gallon is based on the English wine gallon of 231 cubic inches, which was defined by Queen Anne in 1707. When Britain adopted the Imperial gallon in 1824 (based on water weight), the US retained the older wine gallon standard.
Common mistakes
Confusing US gallons with Imperial gallons: a US gallon is about 3.785 litres while an Imperial gallon is about 4.546 litres—roughly 20% larger. This causes major confusion when comparing fuel economy between US and UK figures.
What is US fluid ounce?
A US fluid ounce is a volume unit equal to approximately 29.57 millilitres. It is used in the United States for beverage servings, cooking measurements, and product labelling.
Real-world uses
US fluid ounces are used for beverage labelling (a standard can of soda is 12 fl oz), cooking measurements, and cosmetics packaging in the United States. Cocktail recipes and bartending rely heavily on fluid ounce measurements (a standard shot is 1.5 fl oz).
History
The US fluid ounce derives from the English wine gallon tradition. When the US and UK diverged in measurement standards in the 19th century, their fluid ounces ended up slightly different. The US fluid ounce is defined as 1/128 of a US gallon.
Common mistakes
Confusing US fluid ounces with Imperial fluid ounces—they differ by about 4% (US: 29.57 mL, Imperial: 28.41 mL). Also, confusing fluid ounces (volume) with avoirdupois ounces (weight), which are completely different measurements.
When is this conversion used?
Fuel economy, beverage volumes, and liquid measurements frequently require converting between litres and US gallons, especially for automotive and cooking contexts across different markets.
Worked examples
1 US gallon = 128 US fluid ounce
1 US fluid ounce = 0.02957353 litre
How to convert US gallon to US fluid ounce
To convert US gallon to US fluid ounce, multiply the value by 128.
To convert US fluid ounce back to US gallon, multiply by 0.0078125.
Measurement standards
The cubic metre is the SI derived unit of volume. The litre, equal to exactly one cubic decimetre (0.001 m³), is accepted by the BIPM for use alongside SI units. Both the lowercase "l" and uppercase "L" are approved symbols for the litre.
Did you know?
An Olympic swimming pool holds 2,500 cubic metres of water — about 2.5 million litres. The Amazon River discharges roughly 209,000 cubic metres per second, enough to fill 84 Olympic pools every single second.
Quick reference: US gallon to US fluid ounce
| US gallon | US fluid ounce |
|---|---|
| 0.1 | 12.8 |
| 0.5 | 64 |
| 1 | 128 |
| 2 | 256 |
| 5 | 640 |
| 10 | 1,280 |
| 25 | 3,200 |
| 50 | 6,400 |
| 100 | 12,800 |
| 250 | 32,000 |
| 500 | 64,000 |
| 1,000 | 128,000 |
Common values
| US gallon | US fluid ounce | |
|---|---|---|
| A teaspoon | 0.00132086 US gallon | 0.16907011 US fluid ounce |
| A cup of coffee | 0.06604301 US gallon | 8.45350568 US fluid ounce |
| A water bottle | 0.13208603 US gallon | 16.90701135 US fluid ounce |
| A bathtub | 79.25161571 US gallon | 10,144.20681055 US fluid ounce |
| A swimming pool (Olympic) | 660,430.13089537 US gallon | 84,535,056.7546075 US fluid ounce |
Available Volume units
More US gallon conversions
- Convert US gallon to litre
- Convert US gallon to millilitre
- Convert US gallon to cubic metre
- Convert US gallon to Imperial gallon
- Convert US gallon to US fluid ounce
- Convert US gallon to Imperial fluid ounce
- Convert US gallon to teaspoon (metric)
- Convert US gallon to tablespoon (metric)
- Convert US gallon to cubic centimetre