imperial gallon
Volumeexact by definition
The imperial gallon is exactly 4.54609 litres. Since 1985 the United Kingdom has defined it as that exact metric value, replacing the older definition based on the mass of water. It divides into 4 imperial quarts, 8 imperial pints or 160 imperial fluid ounces.
Watch out: The imperial gallon is about 20% larger than the US gallon of 3.785 L. It is still seen in British and Commonwealth fuel-economy figures, older marine and aviation documents, and Canadian legacy equipment.
| 1 imp gal | 4.54609 L |
The Weights and Measures Act of 1824 abolished the separate English wine, ale and corn gallons and replaced them with a single gallon defined as the volume occupied by ten pounds of distilled water under specified conditions. That definition made the gallon depend on a weighing, so it was later replaced by the exact litre value in use today.