An imperial fluid ounce is 1/160 of an imperial gallon.
Imperial fluid ounces to Imperial gallons Converter — imp fl oz to imp gal
Convert Imperial fluid ounce (imp fl oz) to Imperial gallon (imp gal) using the exact conversion factor (1 imperial fluid ounce = 0.00625 imperial gallon). See the formula, worked examples, conversion table, unit comparison, history, and common uses.
Imperial fluid ounces to Imperial gallons converter
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Context values
Some unit families need one extra value for a physically accurate result.
An imperial gallon is exactly 4.54609 liters.
Result = input x 2.84130625e-5 / 0.00454609.
Volume uses the cubic meter as the base unit.
Reserved above the conversion cards and below the converter.
About Converting Imperial fluid ounces to Imperial gallons
Imperial fluid ounce and Imperial gallon appear side by side at fuel pumps and on beverage labels, since the US measures liquids in gallons while most of the world uses liters. Imperial fluid ounce is typically associated with united Kingdom (historically; less common in current UK retail than metric units), while Imperial gallon is typically associated with united Kingdom, Canada (some contexts), and other Commonwealth countries.
Formula
imperial gallons = imperial fluid ounces × 0.00625
This factor comes from each unit's defined relationship to the category's base unit: 1 imperial fluid ounce equals 0.0000284130625 base units, and 1 imperial gallon equals 0.00454609 base units, so dividing one by the other gives the direct imperial fluid ounce-to-imperial gallon factor of 0.00625.
Simple example
1 imp fl oz × 0.00625 = 0.00625 imp gal
1 imperial fluid ounce = 0.00625 imperial gallons.
Real-world example
10 imp fl oz × 0.00625 = 0.0625 imp gal
10 imperial fluid ounces = 0.0625 imperial gallons.
Conversion table
| Imperial fluid ounce (imp fl oz) | Imperial gallon (imp gal) |
|---|---|
| 1 imp fl oz | 0.00625 imp gal |
| 5 imp fl oz | 0.03125 imp gal |
| 10 imp fl oz | 0.0625 imp gal |
| 25 imp fl oz | 0.15625 imp gal |
| 50 imp fl oz | 0.3125 imp gal |
| 100 imp fl oz | 0.625 imp gal |
Reverse conversion: Imperial gallon to Imperial fluid ounce
0.00625 imp gal × 160 = 1 imp fl oz
0.00625 imperial gallons = 1 imperial fluid ounce.
imperial fluid ounces = imperial gallons × 160
For a page dedicated to this direction, see Imperial gallon to Imperial fluid ounce.
Imperial fluid ounce vs. Imperial gallon
| Aspect | Imperial fluid ounce | Imperial gallon |
|---|---|---|
| Family | UK/imperial customary unit | UK/imperial customary unit |
| Typical use | UK/Commonwealth beverage measurement in historical or specialized contexts | UK fuel and beverage measurement (historically; UK now primarily uses liters for retail) |
| Where it's used | United Kingdom (historically; less common in current UK retail than metric units) | United Kingdom, Canada (some contexts), and other Commonwealth countries |
Understanding the Imperial fluid ounce
Imperial fluid ounce (imp fl oz) measures volume. The imperial fluid ounce is 1/160 of an imperial gallon: exactly 28.4130625 milliliters — slightly smaller than the US fluid ounce despite the larger imperial gallon, because it divides that gallon into more parts. It is classified as a UK/imperial customary unit.
Where it's used: United Kingdom (historically; less common in current UK retail than metric units)
Imperial fluid ounce vs. US fluid ounce. Confusingly, the imperial fluid ounce (28.41 mL) is slightly smaller than the US fluid ounce (29.57 mL), even though the imperial gallon is larger overall — because the imperial gallon is divided into 160 fluid ounces rather than the US gallon's 128.
Uses of the Imperial fluid ounce today
- UK/Commonwealth beverage measurement in historical or specialized contexts
History of the Imperial fluid ounce
The imperial fluid ounce follows from Britain's 1824 imperial gallon, divided into 160 parts rather than the 128 used in the US system, producing its counterintuitively smaller size relative to the US fluid ounce.
Historical origin. Imperial fluid ounce was not the invention of a single named person; it developed through the process described above.
Understanding the Imperial gallon
Imperial gallon (imp gal) measures volume. The imperial gallon is defined as exactly 4.54609 liters, about 20% larger than the US gallon. It is classified as a UK/imperial customary unit.
Where it's used: United Kingdom, Canada (some contexts), and other Commonwealth countries
Imperial gallon vs. US gallon. Britain's 1824 Weights and Measures Act defined a new gallon based on 10 pounds of water, replacing the old wine gallon the US had already adopted — leaving the US (3.785 L) and imperial (4.546 L) gallons about 20% apart today.
Uses of the Imperial gallon today
- UK fuel and beverage measurement (historically; UK now primarily uses liters for retail)
- Commonwealth country liquid measurement in some contexts
History of the Imperial gallon
The imperial gallon was created by Britain's Weights and Measures Act of 1824, defined as the volume of 10 pounds of water, replacing several inconsistent older English gallon definitions (wine gallon, ale gallon, corn gallon) with one standard.
Historical origin. Imperial gallon was not the invention of a single named person; it developed through the process described above.
Imperial fluid ounce — sources
- UK Weights and Measures Act 1824 — Basis for the imperial fluid ounce via the imperial gallon.
Imperial gallon — sources
- UK Weights and Measures Act 1824 — Establishes the imperial gallon definition.
Reserved between the cards and the FAQ so the page stays balanced.
Frequently asked questions
How many imperial gallons are in 1 imperial fluid ounce?
1 imperial fluid ounce equals 0.00625 imperial gallons, using the exact defined conversion factor rather than an estimate.
How do I convert imperial fluid ounce to imperial gallon?
Multiply the imperial fluid ounce value by 0.00625. The converter above does this instantly to whatever precision you set.
How do I convert imperial gallon back to imperial fluid ounce?
Use the reverse factor: 1 imperial gallon equals 160 imperial fluid ounces. You can also use the swap control in the converter above to flip the direction instantly.
What is a imperial fluid ounce?
Imperial fluid ounce (imp fl oz) measures volume. The imperial fluid ounce is 1/160 of an imperial gallon: exactly 28.4130625 milliliters — slightly smaller than the US fluid ounce despite the larger imperial gallon, because it divides that gallon into more parts. It is classified as a UK/imperial customary unit.
What is a imperial gallon?
Imperial gallon (imp gal) measures volume. The imperial gallon is defined as exactly 4.54609 liters, about 20% larger than the US gallon. It is classified as a UK/imperial customary unit.
Is the imperial fluid ounce to imperial gallon conversion exact?
Yes. The imperial gallon is defined as exactly 4.54609 liters, about 20% larger than the US gallon. That fixed definition is what the converter above uses, so any rounding you see is a display choice, not a limitation of the math.
What is the difference between imperial fluid ounce vs. us fluid ounce?
Confusingly, the imperial fluid ounce (28.41 mL) is slightly smaller than the US fluid ounce (29.57 mL), even though the imperial gallon is larger overall — because the imperial gallon is divided into 160 fluid ounces rather than the US gallon's 128.
Where is the imperial fluid ounce still used today?
United Kingdom (historically; less common in current UK retail than metric units)