Severity Rate Calculator

Frequently Asked Questions About Severity Rates

What Is a Severity Rate?

The severity rate measures the impact of workplace injuries by calculating the number of lost workdays per 100 full-time employees. Unlike TRIR which counts the number of incidents, the severity rate captures how serious those incidents are by measuring the total days of productive work that were lost.

What Is the Severity Rate Formula?

There are two commonly used severity calculations:

• Lost Workday Rate = (Number of Lost Workdays × 200,000) / Total Hours Worked — This normalizes the result per 100 full-time employees per year, making it comparable across companies of different sizes.
• Average Severity Per Incident = Total Lost Workdays / Number of Recordable Incidents — This tells you the average number of days lost per incident, helping you understand how serious a typical injury at your facility is.

What Counts as a Lost Workday?

A lost workday is any day (following the day of injury) that an employee cannot work due to a work-related injury or illness. Key rules include:

• Do not count the day of injury or onset of illness — begin counting on the following day.
• Count any day a physician or licensed healthcare professional recommends the employee stay off work, regardless of whether the employee chooses to come in anyway.
• Count weekends, holidays, and other scheduled days off if the employee would not have been able to work on those days.
• If an employee cannot get to work because of the injury (e.g., in a cast and cannot drive), those days count even if work is available.
• Cap the count at 180 days per case unless the employee has permanently left employment, per OSHA recordkeeping rules.

Do Restricted Duty Days Count as Lost Workdays?

Restricted duty days and days away from work are tracked separately on the OSHA 300 log. For the lost workday rate, organizations typically include only days away from work. However, some companies include restricted duty days for a more comprehensive view of injury impact. The most important thing is to be consistent in your methodology when comparing across time periods or facilities.

What Is the Difference Between Severity Rate and TRIR?

TRIR measures frequency — how often recordable incidents occur. The severity rate measures impact — how many workdays are lost from those incidents. A company could have a low TRIR but a high severity rate if its few incidents result in many lost days (e.g., serious fractures or amputations), or a high TRIR but low severity rate if incidents are numerous but minor. Using both metrics together provides a more complete safety picture.

What Is the Difference Between Severity Rate and DART Rate?

The DART rate counts the number of incidents that result in days away, restricted work, or transfers. The severity rate measures the total number of lost workdays from those incidents. DART tells you how many incidents caused lost time; the severity rate tells you how much time was actually lost.

Why Is the Severity Rate Important?

The severity rate reveals the true cost and impact of workplace injuries that incident counts alone cannot show:

• Financial impact — Lost workdays directly correlate with workers' compensation costs, overtime for replacement workers, and lost productivity.
• Hazard identification — A rising severity rate may indicate that while incidents are less frequent, the ones that do occur are more serious, pointing to unaddressed high-consequence hazards.
• Insurance costs — Workers' compensation insurance premiums are heavily influenced by the severity and cost of claims, not just frequency.
• Regulatory attention — OSHA considers both frequency and severity when evaluating an employer's safety performance and targeting inspections.

How Do I Lower My Severity Rate?

Reducing the severity rate requires both preventing serious injuries and improving outcomes when injuries do occur:

• Early return-to-work programs — Offer modified or transitional duty assignments so employees can return safely while recovering.
• Prompt medical care — Ensure injured employees receive timely, quality medical treatment to reduce recovery time.
• Root cause analysis — Investigate incidents thoroughly to identify and eliminate the hazards that cause the most serious injuries.
• Trend analysis — Use incident reporting software to identify patterns in high-severity injuries by location, activity, time of day, and other factors.
• Medical provider partnerships — Work with occupational health clinics that understand return-to-work goals and avoid unnecessary treatments that extend lost time.

What Hours Should I Include?

"Hours worked" should include all employee work hours (including supervised non-employees) over a 12-month period, but not hours such as vacation, sick leave, holidays, etc. (even if paid). If actual hours are unavailable for employees paid on commission, by salary, or by the mile, hours may be estimated based on scheduled hours or 8 hours per workday.

How Do I Calculate the Severity Rate For a Specific Month?

Use 16,667 in the formula instead of 200,000. This normalizes your severity rate for 100 full-time employees per month instead of per year.

What Other Free Safety Calculators Do You Have?

Click on the links below to view our other calculators:

• TRIR Calculator — Calculate your Total Recordable Incident Rate
• DART Rate Calculator — Calculate your Days Away, Restricted, or Transfer rate
• Injury Cost Calculator — Estimate the true financial cost of workplace injuries
Heat Index Calculator

Who Can I Ask for Help With OSHA Recordkeeping?

In addition to offering EHS Incident Reporting Software to help track and manage injuries and illnesses, our company also provides OSHA Recordkeeping assistance in the form of expertise, OSHA recordkeeping reviews, and OSHA recordkeeping form preparation. Please call us at (720) 547-5102 to learn more.

How Incident Reporting Software Can Help Reduce Severity

Incident Reporting Software streamlines and simplifies your processes for reporting, tracking, and investigating incidents. When it comes to reducing your severity rate specifically, software helps by: