What is the formula to calculate retention rate?

The formula for calculating retention rate is accurately represented by the option stating that you take the number of customers at the end of a period, subtract the number of new customers acquired during that period, and then divide that number by the number of customers at the start of the period.

This formula effectively measures how well a business retains its existing customers over a specific time frame. By taking the total customers at the end of the period and removing the new customers, you are left with only the customers who were retained from the start. Dividing this number by the initial number of customers provides a clear percentage that reflects retention, allowing businesses to assess their customer loyalty and satisfaction levels.

The other options do not provide a correct method for calculating retention rate, as they either involve incorrect permutations of the figures or misunderstand the relationships between customers over the specified time period. Hence, option A accurately outlines the calculation needed for determining retention rate.