Hoppus

The hoppus cubic foot (or ‘hoppus cube’ or ‘h cu ft’) was the standard volume measurement used for timber in the British Empire and countries in the British sphere of influence before the introduction of metric units. It is still used in the hardwood trade of some countries. This volume measurement was developed to estimate what volume of a round log would be usable timber after processing, in effect attempting to ‘square’ the log and allows for waste. The hoppus ton (HT) was also a traditionally used unit of volume in British forestry. One hoppus ton is equal to 50 hoppus feet or 1.8027 cubic meters. Some shipments of tropical hardwoods, especially shipments of teak from Myanmar (Burma), are still stated in hoppus tons.

History
The English surveyor Edward Hoppus introduced the eponymous unit in his 1736 manual of practical calculations.

Calculation of timber volume in round logs
The following calculation can be used to estimate the usable timber in round logs:

Hoppus Volume (hft) = (Mid Quarter Girth in ins.)^2 X Length (ft) / 144

One hoppus foot = 1.273 true ft3; 27.74 h ft = 1 m3; and 1 h ft = 0.03605m3. A hoppus foot is approximately 21% oversize compared with a true cubic foot.