Churn rate is expressed as a percentage. You can calculate churn rate by taking the total number of lost users over a given time period divided by the number of users you started with at the beginning of that time period and multiplying by 100. Written as a formula, that looks like:
# of lost users at the end of the time period/# of users at the beginning of the time period X 100 = % Churn Rate
For example, let’s say you want to calculate your churn rate over a 10-day period. You have 20 users on day one and 12 users on day 10. By subtracting 12 from 20, you’ll find that you lost eight users over the 10-day period.
8/20 x 100 = 40% churn rate