Attrition Rate

What is attrition rate?

Attrition rate is the percentage of an organization's workforce lost in a period through departures that are not backfilled, calculated by dividing those departures by the average headcount for the period. It measures how fast a workforce is shrinking, which is why it is read alongside the turnover rate rather than in place of it.

Key facts

• Also called: Employee attrition rate, staff attrition rate, natural attrition
• Measured as: (Departures not backfilled ÷ average headcount) × 100, for a defined period
• Usual period: Quarter or year; annual is the usual comparison figure
• Differs from: Turnover rate, which counts all separations whether or not the role is refilled
• Owned by: HR or People Operations, with Finance for headcount planning

How to calculate attrition rate

The formula has three inputs: the number of people who left during the period and were not replaced, the headcount at the start, and the headcount at the end.

Attrition rate = (departures not backfilled ÷ average headcount) × 100

Average headcount = (headcount at start + headcount at end) ÷ 2

The phrase "not backfilled" carries the whole definition. A resignation where the role is reposted and refilled is turnover. A resignation where the role is left open or eliminated is attrition. Because a backfill decision can change later, many teams fix a cut-off, such as the end of the period, and count the role as not backfilled if it is still open or closed at that point.

Worked example

The numbers below are an illustration, not a benchmark.

A company starts the year with 240 employees and ends it with 260. During the year 20 people leave. Fifteen of the roles are reposted and refilled; five are closed.

Average headcount = (240 + 260) ÷ 2 = 250

Attrition rate = (5 ÷ 250) × 100 = 2 percent

For comparison, the turnover rate for the same year counts all 20 leavers: (20 ÷ 250) × 100 = 8 percent.

Types of attrition

Attrition is sorted by why the role was not refilled, because that is what the number is meant to reveal.

Voluntary attrition is an employee's departure where the employer decides not to replace them. Involuntary attrition is an employer-initiated departure, such as a layoff, where the role is removed. Retirement attrition is departure at the end of a career where the role is not refilled; retirements are the most predictable attrition to plan for. Structural attrition is the deliberate kind: roles are eliminated or merged, so departures are not backfilled on purpose.

Planned attrition through retirements or restructuring can be healthy when a team is resizing. Unplanned attrition in a team that was meant to grow is a warning sign that hiring is not keeping pace with departures.

Employee attrition and attrition rate

Employee attrition is the event: people leaving and not being replaced, so the organization shrinks. Attrition rate is the measurement of that event over a period. In everyday use "attrition" is sometimes used for any departure at all, and departures that are not refilled are sometimes called natural attrition. In this glossary the narrower meaning applies, because it is what makes the number useful for workforce planning: it tells you how much of your headcount is leaving without a plan to replace it.

Attrition rate and turnover rate

The two rates share a denominator and differ in the numerator. Turnover rate counts every separation; attrition rate counts only separations that were not backfilled. A team can show high turnover and almost no attrition, because every exit is refilled, or low turnover that is almost all attrition, because the few leavers are not replaced. The live entry on attrition rate vs. turnover rate sets the two side by side with a second example, and the turnover rate entry (add link when published) carries the turnover formula, its conventions, and a national reference point.

How to reduce attrition

Reducing attrition starts with the backfill decision. Review every open role that has passed its cut-off and record why it was left open: budget, a hiring freeze, a role that no longer fits the plan, or a search that stalled. Where the role is still needed, raise the requisition and source it. Where it is not, close it on purpose and update the workforce plan. Track expected retirements ahead of time and start succession or sourcing early, before the role sits empty.

Why attrition rate matters for recruiting

Attrition is the part of workforce change that does not reach the recruiting team, because no requisition is filled. That makes it a number to watch for what it hides. A rising attrition rate in a team with growth targets means roles are being closed rather than filled. A falling attrition rate alongside a steady turnover rate means more departures are being backfilled, which is more requisitions on the way. Exit interviews and a succession plan turn predictable attrition, such as retirements, into hiring that can be sourced ahead of time. The employee retention entry covers the other side of the ledger, the people who stay.