Attrition Rate Calculator
Measure how fast employees leave. Enter headcount at the start and end of the period, the number of separations during it, and whether the period is a month, quarter, or year — you get the attrition rate, an annualized figure, and average headcount.
Example: with Headcount at start of period 250 · Headcount at end of period 240 · Separations during the period 5 · Period length Month → Attrition rate: 2.04% for the period.
- Annualized rate24.5% per year (simple x12)
- Average headcount245 employees
Computed by the calculator below using its default values. Change any input to see your own numbers.
Attrition rate = separations ÷ average headcount × 100, with average headcount = (start + end) ÷ 2 — the standard SHRM-style convention.
How to calculate attrition rate
Attrition rate is separations divided by average headcount, times 100. Average headcount smooths growth or shrinkage during the period: (start + end) ÷ 2. Losing 5 people in a month while headcount slid from 250 to 240 gives 5 ÷ 245 = 2.04% monthly attrition — about 24.5% a year if the pace holds. HR teams usually count all separations for attrition, then split voluntary versus involuntary when diagnosing causes.
Attrition and turnover use the same formula; the difference is intent. Turnover usually includes backfilled exits, while attrition often refers to departures the company does not refill (retirements, eliminated roles) — definitions vary by organization, so state yours when reporting. Whatever the label, the denominator convention matters: some teams use a 12-month average of monthly headcounts instead of a two-point average, which shifts the number slightly.
Reading your rate
A monthly rate quietly compounds: 2% a month is not 24% of your starting team over a year but slightly less on a retention basis (1 − 0.98¹² = 21.5%), because each month's losses come from a smaller base. The simple ×12 annualization shown here is the common HR convention and is fine for dashboards; just do not mix the two methods when comparing periods. Rising attrition costs show up in recruiting, ramp time, and lost knowledge — benchmark against your own trailing year first, then your industry.
How it’s calculated
Average headcount = (start + end) ÷ 2. Attrition rate = separations ÷ average headcount × 100. Annualized = period rate × 12 for months, × 4 for quarters, × 1 for years (simple multiplication, the common HR convention — compounding version is 1 − (1 − m)¹²).
Uses a two-point headcount average; organizations with strong mid-period swings or seasonal staffing get a truer denominator from monthly averages.
Monthly attrition annualized, two conventions
| Monthly rate | Simple ×12 | Compounded 1−(1−m)¹² |
|---|---|---|
| 1% | 12% | 11.36% |
| 1.5% | 18% | 16.59% |
| 2% | 24% | 21.53% |
| 3% | 36% | 30.62% |
Computed: simple = monthly × 12; compounded = 1 − (1 − monthly)¹²; rounded to two decimals.
Common mistakes
- Dividing by starting headcount instead of the average — in a shrinking team that understates the true rate.
- Counting internal transfers or leaves of absence as separations; only true exits belong in the numerator.
- Annualizing by ×12 and then comparing against a compounded benchmark — pick one convention and label it.
- Mixing timeframes: separations from the whole quarter over a single month's headcount average.
Frequently asked questions
What is the attrition rate formula?
Attrition rate = separations ÷ average headcount × 100, where average headcount = (start + end) ÷ 2. Five exits from an average of 245 employees is 2.04%.
What is the difference between attrition and turnover?
Same math, different scope. Turnover typically counts all exits, backfilled or not; attrition often means exits that are not replaced, like retirements or eliminated roles. Companies vary, so define the term when you report it.
How do I annualize a monthly attrition rate?
The common convention multiplies by 12: 2.04% monthly reports as 24.5% annualized. The compounding-accurate version is 1 − (1 − 0.0204)¹² = 21.9%, slightly lower because each month draws from a smaller base.
What is a good attrition rate?
It varies widely by industry — retail and hospitality run far higher than engineering or government. Benchmark against your own recent history and your sector's published figures rather than a universal number, and watch the voluntary share specifically.