People and HR
Attrition rate
- People and HR
Definition
The percentage of employees who leave an organisation over a period, for any reason, compared with the average number employed.
Also called
Attrition
For your role
Choose your role to see what this term means in your work.
Why it matters
Replacing people costs money and time and disrupts teams. Watching the rate by team and reason shows where retention work will pay off.
Where it is used
HR dashboards, workforce plans and board people reports. Used by HR business partners, people analysts, HR directors and line managers.
How to calculate it
Attrition rate % = leavers in period ÷ average headcount in period × 100
Annualised rate = period rate × (12 ÷ months in period)
Worked example
From January to September 2025, 15 employees left Raket Parts B.V. (employment records with an end date in that period). Average headcount over the period was 406.7 (month-end counts from 404 to 410). Attrition rate = 15 / 406.7 x 100 = 3.7% for nine months, or about 4.9% annualised (3.7% x 12 / 9).
Raket Parts B.V. is a fictional company created for Insyt.
Definitions vary. Some organisations count every leaver; others exclude retirements, end of fixed-term contracts, redundancies or internal moves. The average headcount can be a simple start and end average or a monthly average. Check how your organisation calculates it.