Enter total Lost Time Injuries (LTI) or Recordable Incidents.
Hours worked must be greater than zero.
200,000 (OSHA / 100 Employees)
1,000,000 (International / 500 Employees)
The constant used to normalize data (OSHA typically uses 200,000).
Calculated Frequency Rate
0.00
function calculateFrequency() {
// Get Input Values using var
var incidentsInput = document.getElementById("incidentCount");
var hoursInput = document.getElementById("totalHours");
var factorSelect = document.getElementById("scaleFactor");
var resultBox = document.getElementById("result-container");
var hoursError = document.getElementById("hoursError");
// Parse values
var incidents = parseFloat(incidentsInput.value);
var hours = parseFloat(hoursInput.value);
var factor = parseFloat(factorSelect.value);
// Reset error state
hoursError.style.display = "none";
hoursInput.style.borderColor = "#ced4da";
// Validation
if (isNaN(incidents) || incidents < 0) {
incidents = 0; // Default to 0 if empty
}
if (isNaN(hours) || hours <= 0) {
hoursError.style.display = "block";
hoursInput.style.borderColor = "#dc3545";
resultBox.style.display = "none";
return;
}
// Calculation Logic: (Incidents * Factor) / Hours
var frequencyRate = (incidents * factor) / hours;
// Formatting result
var formattedRate = frequencyRate.toFixed(2);
// Determine context string based on factor
var factorText = (factor === 200000) ? "100 full-time employees" : "500 full-time employees";
// Display Results
document.getElementById("frequencyResult").innerHTML = formattedRate;
var explanationText = "This means there were " + formattedRate + " incidents for every " + factor.toLocaleString() + " hours worked (roughly equivalent to " + factorText + " working for one year).";
document.getElementById("resultExplanation").innerHTML = explanationText;
resultBox.style.display = "block";
}
function resetCalculator() {
document.getElementById("incidentCount").value = "";
document.getElementById("totalHours").value = "";
document.getElementById("scaleFactor").value = "200000";
document.getElementById("result-container").style.display = "none";
document.getElementById("hoursError").style.display = "none";
document.getElementById("totalHours").style.borderColor = "#ced4da";
}
Understanding Frequency Rate Calculations (LTIFR & TRIFR)
In the field of Occupational Health and Safety (OHS), calculating frequency rates is the standard method for quantifying safety performance. Unlike raw incident counts, a Frequency Rate normalizes the data against the total number of hours worked, allowing companies of different sizes to compare their safety records objectively.
What is the Frequency Rate Formula?
The standard formula used by OSHA (Occupational Safety and Health Administration) and many international bodies depends on a scaling factor. The calculation determines the number of incidents that occur per a specific number of hours worked.
Frequency Rate = (Number of Incidents × Scaling Factor) / Total Hours Worked
The Variables Explained
Number of Incidents: This is typically the count of Lost Time Injuries (LTIs) for LTIFR, or the total number of recordable injuries for TRIFR.
Total Hours Worked: The sum of all actual hours worked by all employees during the reporting period (including overtime, excluding leave/vacation).
Scaling Factor:
200,000: The OSHA standard. It represents 100 employees working 40 hours a week for 50 weeks (100 × 40 × 50 = 200,000).
1,000,000: Often used in international standards or by larger organizations. It represents 500 employees working a standard year.
Types of Frequency Rates
While the math remains the same, the input for "Number of Incidents" changes based on the metric you are tracking:
1. LTIFR (Lost Time Injury Frequency Rate)
This metric measures the frequency of injuries that result in an employee missing time from work (usually one day or shift following the incident). It is a key indicator of high-severity incidents.
2. TRIFR (Total Recordable Injury Frequency Rate)
Also known as TRIR, this is a broader metric. It includes Lost Time Injuries, but also Restricted Work Cases (RWC) and Medical Treatment Cases (MTC). It provides a more comprehensive view of the overall safety climate, capturing lower-severity incidents that LTIFR might miss.
Example Calculation
Imagine a manufacturing company with the following data for the year:
Incidents: 3 Lost Time Injuries.
Employees: 150 full-time staff.
Total Hours Worked: 300,000 hours.
Using the OSHA standard factor of 200,000:
(3 × 200,000) / 300,000 = 600,000 / 300,000 = 2.0
This result means that for every 100 employees, there were 2.0 lost time injuries during that period.
Why is this Calculation Important?
Tracking frequency rates allows safety managers to identify trends over time. If your LTIFR is increasing while your total hours remain constant, it indicates a deteriorating safety culture or gaps in hazard controls. Conversely, a declining rate validates the effectiveness of safety training and interventions.