The core recovery is the proportion of core recovered to the total length of the drilled run. The core run is the length reported by the driller as the actual depth penetrated. The core recovery includes both the solid core and the non-solid (or non-intact) core.
The recovery is measured in the field using a tape measure and the records are made as lengths (not calculated as ratios), and this length is entered into the borehole log program. The program then carries out the calculation and expresses the recovery as a percentage on the borehole log.