Historic Gallons to Litres
The gallon size has changed over the centuries. When interpreting historic beers it is important to use the correct liquid volume. N.B The American gallon is the old English wine gallon.
| Date | Gallon | Cubic Inches | % of Imp. Gallon | Litres |
| 1601 | Wine/Troy? | 231 | 83.267% | 3.7854119 |
| 1601 | Ale | 282 | 101.65% | 4.62115205 |
| 1824 | Imperial | 276.8 | 4.5359393 | |
| 1976 | Imperial | 277.42 | 4.54609 |