Enter the number of workdays lost and the total hours worked into the calculator to determine the severity rate.

Severity Rate Formula

The following formula is used to calculate a severity rate.

SR = (DL *200,000) / EHW
  • Where SR is the severity rate
  • DL is the number of work days lost
  • EHW is the employee total hours worked

To calculate a severity rate, multiply the number of work days lost by 200,000, then divide the the total employee hours worked.

Note that this specific formula assumes the time period being analyzed is a year and a sample of 100 workers, hence the average 200,000 hours per year.

Severity Rate Definition

A severity rate is defined as a safety metric used to analyze the severity of workplace injuries by using the number of lost days of work and the total hours worked over a time period.

How to calculate severity rate?

Example Problem #1:

First, determine the number of workdays lost. For this problem, we are looking at a manufacturing company that had a few accidents over the year. This resulted in 5 workdays lost.

Next, determine the total number of hours worked over that same time period. For this example, there were 500,000 work hours.

Finally, calculate the severity rate of the accidents using the formula:

SR = (DL *200,000) / EHW

= (5*200,000) / 500,000

= 2

In this scenario, the severity rate was 2, which is fairly low. This would indicate the accidents that occurred were not major.

Example Problem #2:

In this next problem, the number of workdays lost was found to be much higher at 25 days. However, the total number of hours worked by employees was also higher at 1,000,000 hours.

Using the formula as we did in example #1:

SR = (DL *200,000) / EHW

= (25*200,000) / 1,000,000

= 5.

The severity rate in this second problem was more than 2 times that in the first example, therefore, the accidents in this problem had to be more severe.

severity rate calculator