What is attrition in HR?

The two words are often used interchangeably, but many HR teams draw a line. Turnover counts all leavers, including people who are replaced. Attrition, in the stricter sense, describes the workforce shrinking because leavers are not replaced, as when a company decides not to backfill roles. In India and in many dashboards, “attrition” is simply used to mean employee turnover, so define it in any report you share.

The usual formula for a period is: number of leavers in the period, divided by the average number of employees in the period, multiplied by 100. Average headcount is often taken as the headcount at the start plus the headcount at the end, divided by two. For example, 18 leavers with an average headcount of 240 gives an attrition rate of 7.5% for that period. To annualise a monthly or quarterly rate, use the same period lengths consistently rather than mixing them.

Formula for attrition percentage: attrition rate (%) = (number of leavers in the period ÷ average headcount in the period) × 100. Count only people who left the organisation; internal transfers and promotions are not leavers. Decide in advance whether contractors, interns and fixed-term staff whose contracts simply ended are included, and keep that rule the same in every report.

For an annual attrition rate, add up the leavers across all 12 months and divide by the average headcount for the year (the mean of the 12 month-end headcounts is more accurate than start plus end divided by two when headcount changes a lot). Worked example: a company has 1,180 people at the start of the year and 1,320 at the end, an average of (1,180 + 1,320) ÷ 2 = 1,250, and 150 people left during the year. Annual attrition is 150 ÷ 1,250 × 100 = 12%. A quick way to annualise a single month is to multiply the monthly rate by 12, so 1% in one month projects to about 12% a year, but this assumes every month looks the same.

The same formula gives the sub-rates. Voluntary attrition uses only resignations as the numerator; first-year attrition uses leavers with under 12 months’ service divided by the average number of people with under 12 months’ service. Keep the denominator matched to the group you are measuring, or the percentage will be misleading.

The overall rate hides what you need to act on, so split it. Voluntary versus involuntary attrition, regretted versus non-regretted, and attrition by team, manager, tenure band and role tell very different stories. First-year attrition is especially useful for recruiters, because people leaving in their first months usually point to a mismatch between what was promised and what the job turned out to be, or to a selection problem.

Bringing attrition down usually comes from a mix of better selection (realistic job previews and job-relevant assessment), a structured onboarding, fair pay, a credible career path and good managers. Exit interviews and stay interviews tell you which of those matter most in your organisation.

Also called: attrition rate, employee attrition, staff turnover.