Lost Time Severity Rate Calculator
Measure the impact of safety incidents by calculating workdays lost relative to exposure hours.
What is the Lost Time Severity Rate?
The Lost Time Severity Rate (LTSR) is a safety metric used by Occupational Health and Safety (OHS) professionals to measure the impact of work-related injuries. Unlike the incident rate, which only counts how often accidents happen, the severity rate quantifies how serious those accidents are by looking at the number of workdays lost.
In the United States, the Occupational Safety and Health Administration (OSHA) uses a base of 200,000 exposure hours. This number represents the equivalent of 100 employees working 40 hours per week for 50 weeks in a year.
The LTSR Formula
To calculate the severity rate according to the standard OSHA benchmark, use the following equation:
Why Monitoring Severity Rate Matters
Tracking the LTSR is vital for industrial safety management for several reasons:
- Trend Identification: You may have fewer accidents, but if the ones occurring are more severe, your safety risks are still high.
- Financial Impact: Lost workdays correlate directly with workers' compensation costs and productivity losses.
- Benchmarking: Allows companies to compare their safety performance against industry averages provided by the Bureau of Labor Statistics (BLS).
Example Calculation
Let's say a manufacturing plant has the following data for the calendar year:
| Metric | Value |
|---|---|
| Total Lost Workdays | 60 days |
| Total Employee Hours | 300,000 hours |
| Calculation | (60 × 200,000) / 300,000 |
| Severity Rate | 40.0 |
This result means that for every 100 full-time employees, the company lost 40 workdays due to injuries over the course of the year.
Interpretation of Results
While "good" rates vary significantly by industry (e.g., construction vs. office administration), a rising severity rate is a major red flag. It suggests that while safety protocols might be preventing small cuts or bruises, they are failing to prevent major incidents like falls, crush injuries, or chemical exposures. If your average days lost per injury is high, it may indicate a need for better return-to-work programs or immediate ergonomic interventions.