Incidence Rate Calculation

To calculate the incidence rate for musculoskeletal disorders (MSDs) and cumulative trauma disorders (CTDs) in a workplace, follow these steps:

1. Define the Incidence Rate Formula

The standard formula used by the Occupational Safety and Health Administration (OSHA) to calculate incidence rates is:

Incidence Rate=(Number of Cases×200,000Total Hours Worked)\text{Incidence Rate} = \left( \frac{\text{Number of Cases} \times 200,000}{\text{Total Hours Worked}} \right)Incidence Rate=(Total Hours WorkedNumber of Cases×200,000​)

Where:

• Number of Cases = Total reported cases of MSDs or CTDs within the given period (usually a year).
• 200,000 = A standard base representing 100 full-time employees working 40 hours per week for 50 weeks.
• Total Hours Worked = The sum of all hours worked by employees during the reporting period.

2. Gather Required Data

• Identify the total number of MSD or CTD cases reported in the workplace.
• Determine the total hours worked by all employees in the same time period.

3. Apply the Formula

For example:

• If a company has 12 cases of MSDs in a year and employees worked 500,000 hours, the calculation would be:

Incidence Rate=(12×200,000500,000)=4.8\text{Incidence Rate} = \left( \frac{12 \times 200,000}{500,000} \right) = 4.8Incidence Rate=(500,00012×200,000​)=4.8…