How to Calculate Lost Workday Rate on OSHA 300 Log

The Occupational Safety and Health Administration simplified its lost workday rate calculations in 2002 to improve reporting accuracy. Now known as the days away, restricted or transferred rate, this measurement tracks a company's lost productivity due to workplace injury or illness. Analyze this metric more frequently in large companies or rapidly changing production environments. A sharp increase in your company's DART rate may be an indication you need to improve your safety procedures.

The OSHA 300 log is part of the required reporting for employers. It must contain a detailed record of all injuries and illnesses occurring in the workplace. Keep separate columns for different types of incidents, such as needle sticks, hearing loss and exposure to contagious illnesses. List the type of treatment that was given and the number of days the employee was away from his job as a result of the incident. The employer must record the incident within seven days of being notified of its occurrence and keep all relevant records for at least five years.

Read More: OSHA Form 300A Instructions

The DART rate is based on the percentage of days lost per 100 workers. The calculation depends on the total hours worked for all of the company's employees and how it compares to OSHA's standard annual base hours -- 200,000 hours is the standard base hours worked for 100 people, according to OSHA.

Look at the number of injury or illness incidents recorded in the OSHA 300 log for the applicable period. Count all incidents that resulted in at least one day away from the job or working in a limited capacity. Include transfers to another department if the transfer was due to the employee's inability to perform his normal job duties. Each incident only counts as one for the purposes of this calculation, no matter how many days of work were missed as a result.

For example, consider a company that suffered 20 incidents that resulted in lost work time or a transfer due to limited capabilities. In this example, the total hours worked for the company during the year worked totaled 500,000. To find the company's DART rate, divide the total incidents (20) by the total number of hours worked (500,000) and multiply it by the OSHA standard number of hours (200,000). The result of the calculation is eight incidents per 100 workers.