An important skill to have if you work in the field of health and safety is knowing how to calculate lost time injury frequency rate (LTIFR), among other safety indicators. Although lost time injury frequency rates don't reveal a wealth of information, executives are still eager to know the numbers. We'll discuss why that is at the end of this article, but first we'll go over exactly what this metric is and how to calculate your company's LTIFR.

What Is a Lost Time Injury (LTI)?

A lost time injury (LTI) refers to any injury sustained by a worker that will ultimately lead to the loss of productive work time, either in the form of worker delays or absenteeism.

What Is Lost Time Injury Frequency Rate (LTIFR)?

A frequency rate indicates how many events have happened over a given period by a standardized number of hours worked.

The lost time injury frequency rate, then, refers to the number of lost time injuries that occurred within a given accounting period, relative to the total number of hours worked within the same accounting period.

For the purposes of this definition, injuries are defined as those that occurred in the workplace that resulted in an employee's inability to work the next full work day.

How Is the LTIFR Calculated?

The formula for calculating lost time injury frequency rates is very simple. In many countries, the figure is typically calculated per million hours worked.

The formula: ([Number of lost time injuries in the account period] x 1,000,000) / (Total hours worked in accounting period)

Still confused about calculating LTIFR? Consider this example:

Let’s say your manager wants to know how many lost time injuries occurred over the last year per 1,000,000 hours worked. First, you need to determine the number of LTIs that happened during that period, as well as the number of hours worked. Information regarding the number of LTIs should be readily available from your company’s workers compensation claims manager or insurance company, and data regarding the number of hours worked over the period can be obtained from your company’s payroll section.

After you have obtained the necessary data, multiply the number of lost time injuries by 1,000,000 and then divide the result by the number of hours worked.

And there you have it—the LTIFR.

To make things even clearer, let's use an example that calculates actual numbers.

Say there were eight lost time injuries in the past year and 2,915,638 hours worked. You would start by multiplying the number of LTIs (8) by 1,000,000. Then, you would divide the result by the total number of hours worked (2,915,638), as shown here:

(8 x 1,000,000) / 2,915,638

8 x 1,000,000 = 8,000,000

8,000,000 / 2,915,638 = 2.74

Go ahead and grab a calculator and try it for yourself.

So, you've discovered that your LTIFR is 2.74 but what exactly does that number mean? It means that your company experience 2.74 lost time injuries for every one million hours worked over the past year.

What Injuries Are Considered LTIs?

For an injury to be a lost time injury, it must be an OSHA recordable. A recordable work-related injury is any results in one of the following:

  • Deaths
  • Days away from work
  • Restricted work or transfer to another job
  • Medical treatment beyond first aid
  • Loss of consciousness
  • A significant injury diagnosed by a physician or other licensed healthcare professional

The clearest cases of lost time injuries are those that result in the worker requiring time away from work to recover. But injuries that prevent the worker from performing their regular job duties or require their work duties to be modified for the duration of the recovery are also considered LTIs. So, even if the injured worker still gets to work and punches the clock the next day, their injury might constitute an LTI.

It is also important to note that an injury is only an LTI if it affects the employee's work for at least one full day or shift following the incident. Although work-related injuries typically result in some loss of productivity on the days that they occur, this same-day productivity loss does not count as an LTI.

The most common type of lost time injury are musculoskeletal disorders, such as sprains and strains or muscle tears to the back, shoulder, neck, upper arm, and ankle (learn the Risk Factors for Developing Musculoskeletal Disorders).

Best Practices for Reporting LTIs

Here are a few tips to remember when reporting a lost time injury:

  • All LTIs should be reported verbally within one hour of its occurrence or as soon as possible.
  • A written report should be forwarded to the health and safety representative by the close of business on the same day.
  • The report must be supported by a medical certificate from a registered medical practitioner declaring that the employee is unfit to perform their regular job duties.

Why It's Important to Calculate LTIFRs

Over time, organizations can track their lost time injury frequency rates to help them gauge the effectiveness of their workplace health and safety management systems and programs. Additionally, since regulatory bodies like OSHA use metrics like LTIFR, organizations can benchmark their occupational health and safety performance against OSHA’s statistics for their industry.

While calculating lost time injury frequency rates can have some positive impact on a company’s workplace health and safety, it is in the best interest of an organization to aim to reduce their LTIFRs entirely (see The Journey to Zero! for more on achieving a zero accident rate). This can be achieved first and foremost by avoiding and preventing lost time injuries. For employees, this would mean understanding the need to perform their task safely, and for employers, it means providing their employees with the right equipment and resources to do their jobs in the most efficient, effective, and safe way possible.

For more information on tracking safety metrics, download this safety guide: Leveraging EHS Data to Improve Safety Outcomes.