Formula to Calculate Attrition Rate per Month

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Monthly Employee Attrition Rate Calculator

Include voluntary and involuntary departures.

Monthly Attrition Rate: %

Average Employee Count:

function calculateMonthlyAttrition() { // 1. Get values from inputs var startCountStr = document.getElementById('startCount').value; var endCountStr = document.getElementById('endCount').value; var separationsStr = document.getElementById('separations').value; // 2. Parse to floats var startCount = parseFloat(startCountStr); var endCount = parseFloat(endCountStr); var separations = parseFloat(separationsStr); var resultDiv = document.getElementById('resultOutput'); var percentageSpan = document.getElementById('attritionPercentage'); var avgSpan = document.getElementById('avgEmployeesResult'); // 3. Validate inputs if (isNaN(startCount) || isNaN(endCount) || isNaN(separations) || startCount < 0 || endCount < 0 || separations < 0) { alert("Please enter valid non-negative numbers for all fields."); resultDiv.style.display = 'none'; return; } // Calculate average workforce size var averageEmployees = (startCount + endCount) / 2; // Prevent division by zero if workforce is empty if (averageEmployees === 0) { alert("Average employee count is zero. Cannot calculate attrition rate."); resultDiv.style.display = 'none'; return; } // 4. Calculate Attrition Rate Formula: (Separations / Average Employees) * 100 var attritionRate = (separations / averageEmployees) * 100; // 5. Display results rounded to two decimals percentageSpan.innerHTML = attritionRate.toFixed(2); avgSpan.innerHTML = averageEmployees.toFixed(1); resultDiv.style.display = 'block'; }

Understanding the Formula to Calculate Attrition Rate Per Month

Employee attrition refers to the natural process of employees leaving the workforce through resignation, retirement, or termination. Calculating the monthly attrition rate is a crucial HR metric that helps organizations understand how quickly they are losing talent within a specific 30-day period. High monthly attrition can indicate underlying issues with company culture, compensation, or management.

The Standard Attrition Formula

While there are a few variations, the most widely accepted formula for calculating monthly attrition uses the average number of employees during that month. This approach accounts for fluctuations in hiring and departures throughout the period.

Monthly Attrition Rate (%) = (Total Separations During Month / Average Number of Employees) × 100

To find the Average Number of Employees, you use the following simple calculation:

Average = (Employees at Start of Month + Employees at End of Month) / 2

Component Definitions

  • Start Count: The total headcount on the first day of the month.
  • End Count: The total headcount on the last day of the month.
  • Separations: The total number of employees who left the company during that month for any reason (voluntary or involuntary).

Realistic Example Calculation

Let's say a mid-sized tech company wants to calculate their attrition for November.

  • On November 1st, they had 200 employees (Start Count).
  • During the month, they hired 3 people, but 8 people left the company (Separations).
  • On November 30th, their headcount was 195 (End Count).

Step 1: Calculate the average workforce size.
(200 + 195) / 2 = 395 / 2 = 197.5 average employees.

Step 2: Apply the attrition formula.
(8 separations / 197.5 average) × 100 = 0.0405 × 100 = 4.05%

The company's monthly attrition rate for November was 4.05%.

Why Track This Monthly?

Tracking attrition annually often masks seasonal spikes or immediate reactions to organizational changes. By monitoring the rate monthly, HR departments can spot worrying trends faster—such as a sudden exodus after bonuses are paid out or following a major restructuring—allowing for quicker intervention strategies to retain top talent.

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