function calculateSafetyRate() {
// 1. Get Input Values
var incidentsInput = document.getElementById("numIncidents");
var hoursInput = document.getElementById("totalHours");
var resultBox = document.getElementById("resultContainer");
var rateDisplay = document.getElementById("finalRate");
var explanationDisplay = document.getElementById("resultExplanation");
var incidents = parseFloat(incidentsInput.value);
var hours = parseFloat(hoursInput.value);
// 2. Validation
if (isNaN(incidents) || incidents < 0) {
alert("Please enter a valid number of incidents (0 or greater).");
return;
}
if (isNaN(hours) || hours <= 0) {
alert("Please enter a valid amount of total hours worked (greater than 0).");
return;
}
// 3. Calculation Logic (OSHA Formula)
// Rate = (Incidents * 200,000) / Total Hours
var baseNumber = 200000;
var rate = (incidents * baseNumber) / hours;
// 4. Update UI
resultBox.style.display = "block";
rateDisplay.innerHTML = rate.toFixed(2);
// 5. Dynamic Explanation
var explanationText = "This means for every 100 full-time employees, your company experienced " + rate.toFixed(2) + " recordable incidents/injuries over the specific period.";
explanationDisplay.innerHTML = explanationText;
}
How to Calculate Accident Rate: Understanding TRIR
In the field of Occupational Health and Safety, calculating the "accident rate" usually refers to determining the Total Recordable Incident Rate (TRIR). This metric allows companies of different sizes to compare their safety performance objectively. It normalizes injury data based on the total number of hours worked, ensuring that a large company with many employees isn't unfairly penalized simply for having more staff than a small company.
The Standard Formula
The standard formula used by OSHA (Occupational Safety and Health Administration) and safety professionals worldwide is:
Rate = (Number of Incidents × 200,000) ÷ Total Hours Worked
Here is a breakdown of the variables:
Number of Incidents: The count of work-related injuries and illnesses that required medical treatment beyond first aid (recordable incidents).
Total Hours Worked: The sum of all actual hours worked by all employees (including overtime) during the reporting period. Do not include vacation, sick leave, or holidays.
200,000: This is a constant benchmark number. It represents the equivalent of 100 employees working 40 hours a week for 50 weeks a year (100 × 40 × 50 = 200,000).
Why Use 200,000?
The number 200,000 is used to standardize the rate per 100 full-time employees. By multiplying your incidents by this constant and dividing by actual hours, the result tells you: "If we had exactly 100 employees, how many accidents would we have had?" This makes it possible to compare the safety record of a small construction firm with a massive manufacturing plant.
Example Calculation
Let's look at a practical example using realistic numbers for a mid-sized manufacturing company:
Incidents: The company had 3 recordable injuries this year.
Hours: The total labor hours for all staff was 450,000 hours.
Step 1: Multiply incidents by the constant.
3 × 200,000 = 600,000
Step 2: Divide by total hours.
600,000 ÷ 450,000 = 1.33
The Accident Rate (TRIR) is 1.33. This means there were 1.33 injuries per 100 full-time equivalent workers.
What is a "Good" Accident Rate?
A "good" rate varies significantly by industry. High-risk industries like construction or heavy manufacturing naturally have higher average rates than administrative sectors like finance or insurance.
Generally, a rate below 3.0 is considered average for general industry, while many top-performing companies strive for a rate below 1.0. To evaluate your specific performance, you should compare your calculated TRIR against the NAICS (North American Industry Classification System) average for your specific industry code.
How to Lower Your Rate
Improving your accident rate requires proactive safety management:
Conduct regular safety audits and risk assessments.
Ensure accurate tracking of all labor hours (under-reporting hours artificially inflates your rate).
Implement "Near Miss" reporting to catch hazards before they become recordable incidents.
Invest in ongoing safety training for all personnel.