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 Imperial fluid ounce?
An Imperial fluid ounce is a volume unit used in the United Kingdom equal to approximately 28.41 millilitres. It is used in British cooking recipes, beverage servings, and pharmaceutical labelling.
Real-world uses
Imperial fluid ounces are used in the United Kingdom, Canada (in some contexts), and other Commonwealth countries for beverage serving sizes and recipe measurements. A British pint is 20 Imperial fluid ounces, compared to the US pint of 16 US fluid ounces.
History
The Imperial fluid ounce was defined by the British Weights and Measures Act of 1824, which established the Imperial gallon based on the volume of 10 pounds of water at 62°F. One Imperial fluid ounce is 1/160 of that gallon.
Common mistakes
Assuming Imperial and US fluid ounces are the same. An Imperial fluid ounce is about 28.41 mL versus 29.57 mL for the US version. This means an Imperial pint (568 mL) is larger than a US pint (473 mL).
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 = 133.22786954 Imperial fluid ounce
1 Imperial fluid ounce = 0.02841306 litre
How to convert US gallon to Imperial fluid ounce
To convert US gallon to Imperial fluid ounce, multiply the value by 133.22786954.
To convert Imperial fluid ounce back to US gallon, multiply by 0.00750594.
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 Imperial fluid ounce
| US gallon | Imperial fluid ounce |
|---|---|
| 0.1 | 13.32278695 |
| 0.5 | 66.61393477 |
| 1 | 133.22786954 |
| 2 | 266.45573908 |
| 5 | 666.1393477 |
| 10 | 1,332.27869541 |
| 25 | 3,330.69673852 |
| 50 | 6,661.39347703 |
| 100 | 13,322.78695406 |
| 250 | 33,306.96738516 |
| 500 | 66,613.93477032 |
| 1,000 | 133,227.86954064 |
Common values
| US gallon | Imperial fluid ounce | |
|---|---|---|
| A teaspoon | 0.00132086 US gallon | 0.1759754 Imperial fluid ounce |
| A cup of coffee | 0.06604301 US gallon | 8.79876993 Imperial fluid ounce |
| A water bottle | 0.13208603 US gallon | 17.59753986 Imperial fluid ounce |
| A bathtub | 79.25161571 US gallon | 10,558.52391836 Imperial fluid ounce |
| A swimming pool (Olympic) | 660,430.13089537 US gallon | 87,987,699.31963512 Imperial 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