How to Calculate Attrition Rate (And What It Tells You) - OneSDR

Attrition rate sounds fancy, but it’s just a way of asking:

How many people are leaving your company (or group) over time?

Whether you’re in HR, customer success, or education, attrition rate is a key metric that shows how well you’re retaining people — employees, customers, students, and more.

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🙋 What is Attrition Rate?

Attrition Rate (also called churn rate in some industries) measures the percentage of people who leave a group during a specific period.

You can calculate it monthly, quarterly, or annually — depending on what you want to track.

🧮 Attrition Rate Formula

Here’s the simple formula:

Attrition Rate = (Number of Leavers / Average Number of People) × 100

Where:

Leavers = How many people left during the period
Average Number of People = (Start + End) ÷ 2

✅ Example

Let’s say:

You started the year with 100 employees
Ended with 90
15 people left during the year

👉 Average employees = (100 + 90) ÷ 2 = 95
👉 Attrition rate = (15 / 95) × 100 = 15.79%

So your annual attrition rate is 15.79%.

⚙️ Attrition Rate Calculator

Number of Leavers:
Number at Start of Period:
Number at End of Period:

Attrition Rate: —

📘 Why Does Attrition Rate Matter?

In HR, it helps you monitor employee turnover
In customer service, it shows you how many clients you're losing
In education, it tells you if students are dropping out
In subscriptions, it reflects churn and growth balance

Tracking attrition helps you improve retention, spot red flags, and make better decisions.