Calculate your workplace safety performance based on ANSI Standard Z16.1
Count of Lost Time Injuries (LTI) during the period.
Total actual hours worked by all employees in the reference period.
Disabling Injury Frequency Rate (DIFR)
0.00
injuries per 1,000,000 employee-hours
What is Disabling Injury Frequency Rate (DIFR)?
The Disabling Injury Frequency Rate (DIFR), often referred to as the Lost Time Injury Frequency Rate (LTIFR), is a key safety metric used to measure the number of lost-time injuries occurring in a workplace per 1,000,000 hours worked. It relates the number of injuries to the total amount of work performed, allowing for comparison between organizations of different sizes.
The Formula:
DIFR = (Number of Disabling Injuries × 1,000,000) / Total Employee Hours Worked
Understanding the Inputs
Number of Disabling Injuries: This represents the total number of injuries that resulted in the employee being unable to return to work on their next scheduled shift. This includes temporary total disabilities, permanent partial disabilities, permanent total disabilities, and fatalities.
Total Employee Hours Worked: This is the sum of all actual hours worked by all employees during the specific time period (e.g., monthly, quarterly, or annually). It excludes vacation, leave, or holidays.
The Constant (1,000,000): This standard multiplier represents 500 full-time employees working 40 hours per week for 50 weeks a year (500 employees × 2,000 hours = 1,000,000 hours). Note that while OSHA uses a 200,000 constant for "Incidence Rates," the traditional "Frequency Rate" calculation uses 1,000,000.
Why Calculate DIFR?
Calculating the DIFR helps safety managers and organizations to:
Benchmark Performance: Compare safety performance against industry standards or past performance.
Identify Trends: Determine if safety measures are improving or deteriorating over time.
Normalize Data: Compare the safety records of large companies versus small companies fairly by using the hours worked as a denominator.
Example Calculation
Suppose a construction company had 3 disabling injuries over the course of a year. During that same year, their workforce logged a combined total of 450,000 hours.
This means the company experienced 6.67 disabling injuries for every million hours of work performed.
function calculateDIFR() {
// Get input values
var injuriesInput = document.getElementById('numInjuries');
var hoursInput = document.getElementById('totalHours');
var resultDiv = document.getElementById('difrResult');
var resultValue = document.getElementById('difrValue');
// Parse values
var injuries = parseFloat(injuriesInput.value);
var hours = parseFloat(hoursInput.value);
// Validation
if (isNaN(injuries) || injuries < 0) {
alert("Please enter a valid number of disabling injuries (cannot be negative).");
return;
}
if (isNaN(hours) || hours <= 0) {
alert("Please enter a valid amount of total hours worked (must be greater than 0).");
return;
}
// Calculation logic: (Injuries * 1,000,000) / Hours
var frequencyRate = (injuries * 1000000) / hours;
// Display Result
resultValue.innerHTML = frequencyRate.toFixed(2);
resultDiv.style.display = 'block';
// Scroll to result
resultDiv.scrollIntoView({ behavior: 'smooth' });
}
function resetDIFR() {
document.getElementById('numInjuries').value = '';
document.getElementById('totalHours').value = '';
document.getElementById('difrResult').style.display = 'none';
document.getElementById('difrValue').innerHTML = '0.00';
}