Most turnover rates we get shown are wrong. Not slightly wrong. Wrong by a factor that changes the conclusion. The error is almost always in the denominator.
The formula
Average headcount is (headcount at start + headcount at end) ÷ 2. Not the
December 31 figure. A company that grows from 80 to 120 employees over the year
and records 20 departures has a rate of 20%, not 16.7%.
What counts as a departure
Any permanent exit from payroll: resignation, termination, end of contract, retirement, death. Parental leave, disability leave and internal transfers do not.
Separate voluntary from the rest
A blended rate is useless. Three companies at 18% can be living three completely different situations.
The voluntary rate is the one that measures organizational health. The rest measures your own decisions.
The traps
Check before presenting the number
- Average headcount, not end-of-period headcount.
- Voluntary departures isolated from the total.
- Seasonal roles excluded or calculated separately.
- The same definition year over year. Otherwise the trend means nothing.
What the number does not tell you
A turnover rate is a symptom, not a diagnosis. It tells you something is happening, never what. For that you need three things crossed together: average tenure before departure, the reporting manager, and what the exit interviews say.
A rate climbing from 12% to 19% in one year inside a single team is not an HR problem. It is a management problem, and it has a name.
