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.
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 allow for waste.
The hoppus ton (HT) was also a traditionally used unit of volume in British forestry.
[1] The English surveyor Edward Hoppus introduced the unit in his 1736 manual of practical calculations.
The following calculation can be used to estimate the usable timber in round logs using a "girth tape" that is calibrated in "quarter-girth inches" (e.g. that shows "12" when measuring a 48-inch-circumference log):[4]