How to calculate Employee Turnover Rate

Formula

Turnover rate = leavers in period ÷ average headcount in period × 100

SQL query

This example assumes: employees(id, department, start_date, end_date). It is written in PostgreSQL syntax; date functions differ slightly in MySQL, BigQuery and SQLite, and your column names will differ from these.

WITH hc AS (
  SELECT department,
         (COUNT(*) FILTER (WHERE start_date <= DATE '2026-01-01'
                           AND (end_date IS NULL OR end_date > DATE '2026-01-01'))
        + COUNT(*) FILTER (WHERE start_date <= DATE '2026-12-31'
                           AND (end_date IS NULL OR end_date > DATE '2026-12-31'))) / 2.0 AS avg_headcount,
         COUNT(*) FILTER (WHERE end_date BETWEEN DATE '2026-01-01' AND DATE '2026-12-31') AS leavers
  FROM employees
  GROUP BY department
)
SELECT department, leavers, avg_headcount,
       leavers * 100.0 / NULLIF(avg_headcount, 0) AS turnover_pct
FROM hc
ORDER BY turnover_pct DESC;

Common mistakes that make Employee Turnover Rate wrong

• Using only year-end headcount in the denominator overstates turnover in a shrinking team and understates it in a growing one; use the average.
• Voluntary and involuntary leavers tell different stories; split them.
• Small departments swing wildly with one departure.

Ask for Employee Turnover Rate in plain English

Instead of writing the query yourself, you can type the question. SchemaChat turns it into SQL against your connected database or uploaded file, runs it, and shows the SQL and the figures it used so you can check the answer before you share it. It does not replace your judgement about the definition: check that the query matches the formula your business uses.

• What was employee turnover by department last year?
• How many people left in their first six months?