An imperial gallon is exactly 4.54609 liters.
Imperial gallons to Imperial fluid ounces Converter — imp gal to imp fl oz
Convert Imperial gallon (imp gal) to Imperial fluid ounce (imp fl oz) using the exact conversion factor (1 imperial gallon = 160 imperial fluid ounce). See the formula, worked examples, conversion table, unit comparison, history, and common uses.
Imperial gallons to Imperial fluid ounces converter
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An imperial fluid ounce is 1/160 of an imperial gallon.
Result = input x 0.00454609 / 2.84130625e-5.
Volume uses the cubic meter as the base unit.
Reserved above the conversion cards and below the converter.
About Converting Imperial gallons to Imperial fluid ounces
Imperial gallon and Imperial fluid ounce 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 gallon is typically associated with united Kingdom, Canada (some contexts), and other Commonwealth countries, while Imperial fluid ounce is typically associated with united Kingdom (historically; less common in current UK retail than metric units).
Formula
imperial fluid ounces = imperial gallons × 160
This factor comes from each unit's defined relationship to the category's base unit: 1 imperial gallon equals 0.00454609 base units, and 1 imperial fluid ounce equals 0.0000284130625 base units, so dividing one by the other gives the direct imperial gallon-to-imperial fluid ounce factor of 160.
Simple example
1 imp gal × 160 = 160 imp fl oz
1 imperial gallon = 160 imperial fluid ounces.
Real-world example
10 imp gal × 160 = 1,600 imp fl oz
10 imperial gallons = 1,600 imperial fluid ounces.
Conversion table
| Imperial gallon (imp gal) | Imperial fluid ounce (imp fl oz) |
|---|---|
| 1 imp gal | 160 imp fl oz |
| 5 imp gal | 800 imp fl oz |
| 10 imp gal | 1,600 imp fl oz |
| 25 imp gal | 4,000 imp fl oz |
| 50 imp gal | 8,000 imp fl oz |
| 100 imp gal | 16,000 imp fl oz |
Reverse conversion: Imperial fluid ounce to Imperial gallon
160 imp fl oz × 0.00625 = 1 imp gal
160 imperial fluid ounces = 1 imperial gallon.
imperial gallons = imperial fluid ounces × 0.00625
For a page dedicated to this direction, see Imperial fluid ounce to Imperial gallon.
Imperial gallon vs. Imperial fluid ounce
| Aspect | Imperial gallon | Imperial fluid ounce |
|---|---|---|
| Family | UK/imperial customary unit | UK/imperial customary unit |
| Typical use | UK fuel and beverage measurement (historically; UK now primarily uses liters for retail) | UK/Commonwealth beverage measurement in historical or specialized contexts |
| Where it's used | United Kingdom, Canada (some contexts), and other Commonwealth countries | United Kingdom (historically; less common in current UK retail than metric units) |
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.
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.
Imperial gallon — sources
- UK Weights and Measures Act 1824 — Establishes the imperial gallon definition.
Imperial fluid ounce — sources
- UK Weights and Measures Act 1824 — Basis for the imperial fluid ounce via the imperial gallon.
Reserved between the cards and the FAQ so the page stays balanced.
Frequently asked questions
How many imperial fluid ounces are in 1 imperial gallon?
1 imperial gallon equals 160 imperial fluid ounces, using the exact defined conversion factor rather than an estimate.
How do I convert imperial gallon to imperial fluid ounce?
Multiply the imperial gallon value by 160. The converter above does this instantly to whatever precision you set.
How do I convert imperial fluid ounce back to imperial gallon?
Use the reverse factor: 1 imperial fluid ounce equals 0.00625 imperial gallons. You can also use the swap control in the converter above to flip the direction instantly.
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.
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.
Is the imperial gallon to imperial fluid ounce conversion exact?
Yes. 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. 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 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.
Where is the imperial gallon still used today?
United Kingdom, Canada (some contexts), and other Commonwealth countries