This video shows how to calculate the lifetime value of a customer.

The lifetime value of a customer is the product of the contribution margin ratio, the average length of time that a customer will remain a customer, and the average revenue per customer for the period in question. For example, if the contribution margin ratio is 50% and the average customer remains a customer for 8 months and spends $10 per month, then the lifetime value of a customer would be $40 (50% * 8 * $10).