impairment rating impairment rating an impairment rating is a percentage intended to represent the degree of an individual's impairment, which is a deviation away from one's normal health status and functionality. impairment is distinct from disability. an individual's impairment rating is based on the restrictive impact of an impairment, whereas disability is broadly the consequences one's impairment. impairment ratings given to an individual by different medical examiners are sometimes problematically inconsistent with each other.