How to Compute the Severity Rate in OSHA

Written by tamra spurlock
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How to Compute the Severity Rate in OSHA
A safe workplace has a low OSHA severity rate. (work image by Danil Vachegin from

Severity rate, also known as lost-time workday rate, is used to indicate the gravity of workplace injuries or illnesses. Accident rate alone does not reflect a safe work environment. A company may have a low incident rate, but have a high number of lost work days associated with each incident. A high severity rate is like a red flag, signalling serious safety concerns. The longer it takes an employee to return to work after an accident, the more severe the accident.

Skill level:

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Things you need

  • OSHA Form 300
  • OSHA Form 300A
  • Payroll Records

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  1. 1

    Determine the total number of days away from work. This is the total number of lost-time days due to occupational injury or illness, recorded on line (K) of Occupational Safety and Health Administration (OSHA) Form 300A. You may also obtain this figure by adding the total number of days entered in column (K) of OSHA Form 300.

  2. 2

    Determine the total number of hours worked during the year by all employees. This number is the total of all regular and overtime hours worked, available on OSHA form 300.

  3. 3

    Compute your severity rate. The total number of days away from work times 200,000 (the equivalent of 100 full-time employees working 40 hours per week, 50 weeks per year) divided by the total number of hours worked during the year equals the severity rate. All OSHA rates are expressed as a rate per 100 full-time employees. This provides a standard comparison value so that companies can compare safety performance rates whether they have 50 or 5,000 employees.

Tips and warnings

  • Compare your severity rate with the average for your Standard Industrial Classification (SIC), published annually by the Bureau of Labor Statistics, to assess your safety performance. Bureau of Labor Statistics data can be viewed online at
  • The total number of hours worked during the year should not include vacation, sick leave or holidays.
  • Contact OSHA at (800) 321-OSHA for questions about calculating your severity rate.
  • High severity rates can impact worker compensation costs and insurance premiums.

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