Injury Severity Rate:- It is defined as the number of days lost time because of the injuries per 1000 man hours worked. It is given by-

Injury Severity Rate = No. of days lost* 1000/No. of man hours used

Injury Frequency Rate:- It is defined as the number of disabling injuries per 1000000 man-hours worked. A disabling injury is one which causes loss of working time beyond the day or shift during which the injury was occurred. It is given by-

Injury Frequency Rate = No. of disabling injuries* 1000000/ No. of man-hours worked.

Injury Index: - It gives the overall picture of injuries signifying both frequency and the severity. It is given by-

Injury Index= Frequency Rate* Severity Rate