What is attrition?

When someone leaves and you hire a replacement, the org chart looks the same afterwards. When someone leaves and nobody replaces them, the team is permanently smaller. The second case is attrition in its strict sense: retirements that are not refilled, roles cut in a restructure, vacancies absorbed by a hiring freeze.

In everyday use the word has blurred. Plenty of companies, HR tools and reports say attrition rate when they mean the turnover rate, so check which one a number means before you compare it with anything.

The distinction matters in planning: turnover creates a role to fill, attrition shrinks the team. Many HR teams use the two words interchangeably, so agree internally on which one you mean before comparing numbers with anyone.

Attrition shrinks capacity. Turnover costs you a hiring cycle but leaves capacity intact once the seat is filled again. A plan that treats the two the same will either budget for hiring that is not coming or miss the work the remaining team now has to absorb.

Leavers during the period divided by average headcount for the same period.

The arithmetic is the same as turnover. What changes is which leavers you count: under the strict definition only the exits whose roles were not backfilled, under the loose one every leaver. Write the definition next to the number.

Take an invented team of 50 at the start of the year and 46 at the end. During the year 6 people leave: 4 of the roles are cut or left unfilled, and 2 are backfilled.

Average headcount is (50 + 46) ÷ 2 = 48. Strict attrition counts the 4 unreplaced exits: 4 ÷ 48 × 100, about 8.3%. Turnover counts all 6 leavers: 6 ÷ 48 × 100, which is 12.5%. Both are correct, and they answer different questions.

Letting roles lapse through retirements and resignations is a gentler way to shrink than a layoff. It becomes a problem when it is unplanned: when the roles that disappear are ones the business still needs, and the remaining team quietly absorbs the work.

Published attrition benchmarks rarely say which definition they used, so compare your rate with your own history first.

• Comparing your attrition rate with someone else's without checking whether they count every leaver or only the unreplaced ones.
• Leaving the definition off the report, so next quarter's reader cannot tell which one was used.
• Treating attrition as a free saving. The salary goes away, but the work often stays and lands on the people who remain.
• Counting a role as not backfilled while a hire is still in progress, then never correcting it when the seat is filled.