Attrition rate calculator
Twelve departures with an average headcount of 80 is an attrition rate of 15%. Enter the leavers and the average workforce for any period and get the percentage and the decimal, ready to compare teams or sites. Free in your browser.
- Free
- Runs in your browser
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- Your data stays on your device
Run — free
Worked example
- Departures
- 12
- Average headcount
- 80
- Attrition rate percent
- 15
- Attrition rate decimal
- 0.15
Employee attrition rate is the share of people who left an organization during a defined period, expressed as a percentage of the average number of people employed in that same window. HR business partners, finance controllers, and people-ops analysts use that single figure to compare sites, to flag a team that is emptying faster than it can hire, and to turn a raw exit count into a number boards already recognize. This attrition rate calculator takes two inputs: how many employees departed, and the average headcount over the period. It divides departures by average headcount and multiplies by one hundred, returning the attrition rate as a percentage plus the matching decimal ratio. Zero departures is allowed and yields a zero percent rate.
What attrition rate measures and why average headcount is the denominator
Attrition rate answers a workforce question that raw exit counts cannot: of the people who were typically on the books during a period, what percentage left? Human-resources textbooks and SHRM-style reporting pack that idea into one identity: attrition rate percent equals departures divided by average headcount, times one hundred. Average headcount is the usual denominator because the workforce size changes as people join and leave; using only the opening count or only the closing count would overstate or understate the rate whenever headcount moved a lot during the window.
Departures are the people whose employment ended in that window—resignations, retirements, dismissals, end-of-contract exits, and any other separations your policy treats as leavers. A site that lost twelve people while averaging eighty employees therefore has an attrition rate of fifteen percent, because twelve divided by eighty is zero point one five, and that decimal times one hundred is fifteen. A month with no exits and a strictly positive average headcount has a rate of zero, which is a success, not a missing-data case.
A period in which more people left than the average headcount—high churn with rapid replacement of the same seats—can exceed one hundred percent; that is a valid result, not an error, because the formula is a ratio, not a cap at one hundred. This calculator does not decide who counts as a departure, does not annualize a monthly figure into a yearly rate, does not convert headcount from FTE to heads, and does not compute opening plus closing over two for you.
It applies only the published identity to the two numbers you already have.
Where an attrition rate calculator earns its keep
People-ops and HR business partners need a reproducible attrition percentage so a plant, a store, or a remote team can be compared without each analyst inventing a slightly different denominator. A publisher ranking for attrition rate calculator is targeting people who already have a departure count and an average headcount and want the percentage, not a full workforce forecast, not a resignation-reason taxonomy, and not a retention-program design.
Finance partners who sit in monthly operating reviews need the same number the HRIS printed, so they can challenge a site whose exits look small in absolute terms but large relative to a shrinking average headcount. Classroom and certification courses that teach workforce metrics need an oracle that rejects a zero or negative average headcount and still returns a rate above one hundred percent when churn is extreme, because those two cases are how students confuse the identity with a simple leftover-people percentage.
Engineers writing payroll and people-analytics tests pin known-good pairs—twelve over eighty, a fractional average headcount, and a zero-headcount rejection—so a reporting library cannot silently treat attrition as if it were a count of remaining staff. Failed validation does not consume balance.
What you can do with it
Monthly people-ops scorecards
Enter period departures and average headcount to publish a comparable attrition percentage across plants, stores, or teams without each analyst choosing a different denominator.
Finance operating reviews
Convert an exit count that looks small in absolute terms into a rate against a shrinking average headcount so a site that is emptying is visible in the board pack.
FAQ
How do I calculate employee attrition rate?
Attrition rate percent equals departures divided by average headcount, times one hundred. Example: 12 / 80 × 100 = 15 percent.
What happens if average headcount is zero or negative?
Attrition rate divides by average headcount, so a zero or negative denominator is rejected and is not billed.
Can the attrition rate be greater than 100 percent?
Yes. If more people left than the average number employed in the period (high replacement churn), the ratio exceeds one and the percentage exceeds 100. That is a valid result, not an error.
Does this annualize a monthly attrition figure?
No. The calculator applies the period identity only. If you need an annualized rate, convert with your own convention after you have the period percentage.
Why divide by average headcount instead of the opening headcount?
Because the workforce changes as people join and leave. Using only the opening or only the closing count would overstate or understate the rate whenever headcount moved a lot during the period.
Related tools
For developers — API access
Everything on this page is available programmatically. This section is for teams who want to wire it into their own systems; everyone else can just use the tool above.
API endpoint
Prefer to automate it? One authenticated POST creates the task; the result comes back by webhook or a signed link. The same capability also runs here on the web, by email and from Telegram — and soon from our app too.
Call it from your stack
curl -X POST https://api.kit.forhosting.com/fin/attrition-rate \
-H "Authorization: Bearer $KIT_KEY" \
-H "Content-Type: application/json" \
-d '{"departures":12,"average_headcount":80}'const res = await fetch("https://api.kit.forhosting.com/fin/attrition-rate", {
method: "POST",
headers: {
"Authorization": `Bearer ${process.env.KIT_KEY}`,
"Content-Type": "application/json"
},
body: JSON.stringify({
"departures": 12,
"average_headcount": 80
})
});
const { task_id } = await res.json();import os, requests
res = requests.post(
"https://api.kit.forhosting.com/fin/attrition-rate",
headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
json={
"departures": 12,
"average_headcount": 80
},
)
task_id = res.json()["task_id"]<?php
$res = file_get_contents("https://api.kit.forhosting.com/fin/attrition-rate", false, stream_context_create([
"http" => [
"method" => "POST",
"header" => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
"content" => '{"departures":12,"average_headcount":80}',
],
]));
$task = json_decode($res, true);body := bytes.NewBufferString(`{"departures":12,"average_headcount":80}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/fin/attrition-rate", body)
req.Header.Set("Authorization", "Bearer "+os.Getenv("KIT_KEY"))
req.Header.Set("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)Example request
{
"departures": 12,
"average_headcount": 80
}Example response
{
"task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
"type": "fin.attrition_rate",
"status": "queued",
"_links": {
"result": "/tasks/tsk_…/result"
}
}The API is asynchronous: the call returns a task_id immediately and the result arrives by webhook. Polling is capped at 1 req/s per task.
Pricing
Published price — no tokens, no invented credits. A failed task is never charged.
Limits
max_abs | 1000000000000 |
Errors
| HTTP | Code | Meaning |
|---|---|---|
401 | unauthorized | Missing or invalid API key. |
402 | insufficient_balance | Your balance doesn't cover the task price. |
404 | unknown_type | That task type doesn't exist. |
429 | rate_limited | Too many requests. Use the webhook instead of polling. |
Technical notes
Average headcount of zero or a negative value is rejected with invalid_input, because the rate would divide by zero or invert the meaning of a workforce. Successful calls are billed at $0.002; invalid input is not charged.
Input contract, response shape, and validation
Example: twelve departures and an average headcount of eighty yield fifteen percent and a decimal of zero point one five. Prefer bare numbers over formatted strings; percent signs, thousands separators, and currency marks are not parsed. POST a JSON body with two required finite numbers. departures is the count of employees who left during the period; it must be greater than or equal to zero. Aliases leavers, separations, exits, employees_left, left, and number_of_departures are accepted so a payroll export does not need a rename step. average_headcount is the average number of employees over the same period and must be strictly greater than zero, because the attrition rate divides by that average; aliases avg_headcount, headcount, average_employees, avg_employees, and mean_headcount are accepted. Each field may arrive as a JSON number or as a numeric string that matches a strict finite decimal pattern. Absolute values must stay within one trillion so intermediate products remain finite in IEEE double precision on the Worker and in the browser. Missing fields, empty strings, non-finite values, a negative departure count, an average headcount of zero or below, or a value outside those limits fail with invalid_input naming the field and are not billed. On success the body echoes rounded departures and average_headcount, returns attrition_rate_percent as departures over average headcount times one hundred, attrition_rate_decimal as the unscaled ratio, a formula string you can print next to the numbers, a short English message, and ordered substitution steps. Pricing for a successful item is a flat $0.002.
Where an attrition rate calculator earns its keep
Keep requests small, pin the rounded attrition_rate_percent in tests, and you get stable workforce arithmetic for widgets, board packs, and edge workers without standing up a full HRIS of your own.
Integration use cases
Workforce-metrics homework and tests
Students and QA pin twelve-over-eighty as fifteen percent and a zero average headcount as invalid_input, matching the textbook identity exactly.
Technical questions
What does the attrition rate calculator cost?
The browser tool is free. API requests use prepaid KIT balance at $0.002 per successful call; invalid input is not billed.