Tun

What the unit was used for

The tun is the largest of the English wine casks, 252 wine gallons of the pre-1826 measure.

The number 252 was chosen because it divides by 2, 3, 4, 6, 7, 9 and 12, so a tun broke down into pipes, hogsheads, tierces and rundlets without awkward fractions.

The medieval wine trade with Gascony moved in tuns, so the tun became the measure of what a ship could stow, and “tunnage”, later tonnage, first meant the number of tuns a vessel carried.

Edward III levied three shillings of duty on every imported tun, and a full one weighed somewhere around 2240 lb.

Ship tonnage is the tun’s most visible survival, and gross and net tonnage are still volumes rather than weights.

In the system

1 tun = 2 pipes or butts = 4 hogsheads = 252 wine gallons