body {
font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
line-height: 1.6;
color: #333;
max-width: 1200px;
margin: 0 auto;
padding: 20px;
background-color: #f9f9f9;
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.calculator-container {
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padding: 30px;
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How to Calculate Accident Incident Rate (TRIR)
The Accident Incident Rate, commonly known in the safety industry as the Total Recordable Incident Rate (TRIR), is a standardized metric used by OSHA (Occupational Safety and Health Administration) to quantify safety performance. It allows companies of different sizes to compare their safety records fairly by normalizing the data to represent a rate per 100 full-time employees.
The Standard OSHA Formula
The calculation relies on two main data points: the number of recordable injuries/illnesses and the total number of hours worked by all employees. The formula is as follows:
Incident Rate = (Number of Incidents × 200,000) / Total Hours Worked
Understanding the Variables
- Number of Incidents: This is the count of work-related injuries and illnesses that you have recorded on your OSHA 300 Log. This includes fatalities, lost time cases, restricted work cases, and medical treatment beyond first aid.
- Total Hours Worked: This is the sum of all actual hours worked by all employees during the reference year. It should include overtime but exclude vacation, sick leave, and holidays.
- The 200,000 Constant: Many people ask why 200,000 is used. This number represents the equivalent of 100 full-time employees working 40 hours per week for 50 weeks a year (100 × 40 × 50 = 200,000).
What is the DART Rate?
While TRIR measures all recordable incidents, the DART Rate (Days Away, Restricted, or Transferred) is arguably more critical because it measures the severity of workplace injuries. It specifically counts incidents that resulted in an employee missing work, being restricted in their duties, or being transferred to another job.
The formula for DART is identical to TRIR, but you only include incidents that fit the DART criteria in the numerator:
DART Rate = (DART Incidents × 200,000) / Total Hours Worked
Example Calculation
Let's assume a manufacturing company has 150 employees. In one year:
- They recorded 8 injuries.
- The total hours worked by all employees was 310,000 hours.
Step 1: Multiply incidents by the constant.
8 × 200,000 = 1,600,000
Step 2: Divide by total hours worked.
1,600,000 / 310,000 = 5.16
This company has a TRIR of 5.16, meaning for every 100 full-time employees, approximately 5.16 injuries occurred that year.
Why Monitor These Rates?
Calculating your accident incident rate is not just about compliance. It helps safety managers:
- Identify Trends: A rising rate indicates deteriorating safety protocols.
- Benchmark Performance: Compare your rates against Bureau of Labor Statistics (BLS) averages for your specific NAICS industry code.
- Lower Insurance Costs: Better safety rates often translate to lower workers' compensation premiums.
What is a "Good" Incident Rate?
A "good" rate depends entirely on your industry. Construction and manufacturing typically have higher rates than finance or retail. However, the ultimate goal for any safety program is zero accidents. Generally, staying below the industry average published by the BLS is considered a baseline for compliance and safety management.
function calculateSafetyRates() {
// Get input values
var incidentsInput = document.getElementById('totalIncidents');
var dartInput = document.getElementById('dartIncidents');
var hoursInput = document.getElementById('totalHours');
var resultBox = document.getElementById('resultOutput');
// Parse values
var incidents = parseFloat(incidentsInput.value);
var dart = parseFloat(dartInput.value);
var hours = parseFloat(hoursInput.value);
// Validation
if (isNaN(incidents) || incidents < 0) {
alert("Please enter a valid number of incidents.");
return;
}
if (isNaN(hours) || hours incidents) {
alert("DART incidents cannot be higher than Total Recordable Incidents.");
return;
}
// The OSHA Constant
var oshaConstant = 200000;
// Calculations
var trir = (incidents * oshaConstant) / hours;
var dartRate = (dart * oshaConstant) / hours;
// Calculate equivalent full-time employees for context
// Assuming 2000 hours per year per employee
var fte = hours / 2000;
// Display Results
document.getElementById('trirResult').innerHTML = trir.toFixed(2);
document.getElementById('dartResult').innerHTML = dartRate.toFixed(2);
document.getElementById('fteResult').innerHTML = Math.round(fte) + " FTEs";
// Show result box
resultBox.style.display = "block";
}