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).
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.
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 Imperial fluid ounce = 0.00750594 US gallon
1 US gallon = 3.78541178 litre
How to convert Imperial fluid ounce to US gallon
To convert Imperial fluid ounce to US gallon, multiply the value by 0.00750594.
To convert US gallon back to Imperial fluid ounce, multiply by 133.22786954.
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: Imperial fluid ounce to US gallon
| Imperial fluid ounce | US gallon |
|---|---|
| 0.1 | 0.00075059 |
| 0.5 | 0.00375297 |
| 1 | 0.00750594 |
| 2 | 0.01501187 |
| 5 | 0.03752969 |
| 10 | 0.07505937 |
| 25 | 0.18764843 |
| 50 | 0.37529685 |
| 100 | 0.7505937 |
| 250 | 1.87648426 |
| 500 | 3.75296852 |
| 1,000 | 7.50593703 |
Common values
| Imperial fluid ounce | US gallon | |
|---|---|---|
| A teaspoon | 0.1759754 Imperial fluid ounce | 0.00132086 US gallon |
| A cup of coffee | 8.79876993 Imperial fluid ounce | 0.06604301 US gallon |
| A water bottle | 17.59753986 Imperial fluid ounce | 0.13208603 US gallon |
| A bathtub | 10,558.52391836 Imperial fluid ounce | 79.25161571 US gallon |
| A swimming pool (Olympic) | 87,987,699.31963512 Imperial fluid ounce | 660,430.13089537 US gallon |
Available Volume units
More Imperial fluid ounce conversions
- Convert Imperial fluid ounce to litre
- Convert Imperial fluid ounce to millilitre
- Convert Imperial fluid ounce to US gallon
- Convert Imperial fluid ounce to cubic metre
- Convert Imperial fluid ounce to Imperial gallon
- Convert Imperial fluid ounce to US fluid ounce
- Convert Imperial fluid ounce to teaspoon (metric)
- Convert Imperial fluid ounce to tablespoon (metric)
- Convert Imperial fluid ounce to cubic centimetre