Severity rate is a metric used to measure the seriousness of workplace injuries, typically expressed as lost workdays per unit of exposure.
A safety performance metric calculated by dividing the total number of lost workdays due to injury by a standardized measure of hours worked (commonly per 200,000 hours), then scaling the result. It complements incidence rates by capturing how serious injuries are, not just how frequently they occur.
A company with relatively few injuries but several severe cases resulting in extended time off would show a high severity rate, prompting deeper investigation into those specific incidents.
Incidence rate measures how often injuries occur, while severity rate measures how serious those injuries are based on lost workdays, so the two metrics can tell very different stories about the same workplace.
There's no universal benchmark; a good severity rate is typically judged relative to industry averages and a company's own historical trends rather than a fixed number.
Tracking both gives a fuller picture of safety performance — a low-frequency, high-severity pattern may indicate a small number of very dangerous conditions that warrant urgent attention.
Part of SafetyIQ's EHS glossary: plain-English definitions of workplace health and safety terms.
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