It depends on what the commodity is. A hogshead of ale is 54 imperial gallons. Of other liquids, it can vary depending on the liquid. Of solid commodities, such as tobacco, it is different again.
Are we the only country that makes life difficult. Why should wine and beer be different ?
1 lb of sugar = 1lb of butter ...simple... surely ...
Now I need to lie down in a darkened room ! xx