Whole person impairment is a percentage rating of the permanent effect of an injury on your body as a whole, assessed by a doctor trained in the relevant guides. In most injury schemes it decides which heads of damage you can claim and whether you can pursue a common law claim.
The short answer
Whole person impairment, usually shortened to WPI, is a percentage that measures how much a permanent injury affects your whole body rather than the injured part alone. A doctor trained in the relevant impairment guide examines you once your condition has stabilised and records a percentage supported by the guide.
The percentage matters because most injury schemes use it as a gateway. Whether you can claim certain heads of damage, and whether you can pursue a common law claim at all, often turns on reaching a threshold set by the scheme. That makes the assessment a turning point in the matter, not a formality.
Our article on how whole person impairment is worked out explains the assessment in more detail.