My Manager asked me to measure "Churn Rate". Any idea on how to do it?

Churn means the customer is not interested/willing further more to continue in your product. We can measure by checking that how many customers are rolled back from your data base.

 

You may find many formula but you should know the cause of customer lost

In short, a study shows the number of customers you have and how long they are going to be in the company. If you modify or add specific changes to the company's system or service, what are the number of customers who leave the company and the number of new customers who accept this service

Simply it is percentage of customers who are becoming no longer your customers over predefined period of time e.g. quarter, half year, etc...from your total number of customers. Example, company x started q1 with 100 customers, by end of q120 customers terminated their services with the company, then the churn rate is 20%.

What is Churn Rate? The churn rate, also known as the rate of attrition, is most commonly known as the percentage of service subscribers who discontinue their subscriptions within a given time period. It is also the rate at which employees leave their jobs within a certain period. For a company to expand its clientele, its growth rate (measured by the number of new customers) must exceed its churn rate. https://blog.recurly.com/better-way-to-calculate-your-churn-rate

Churn Rate typically refers to the rate of customers that are unsubcribing from membership of a company or dissatisfied with the company and they are currently not active due to some reasons. You can easily measure the churn rate of customers by analysing the sales data of Past and present. From which you can derived the inactive customers and also percentage of present churn rate.

To calculate your probable monthly churn, start with the number of users who churn that month. Then divide by the total number of user days that month to get the number of churns per user day. Then multiply by the number of days in the month to get your resulting monthly churn rate .  the number of new customers must exceed its churn rate