This is calculated by dividing total revenue from subscriptions by the total number of subscribers.
ARPU is a metric used by companies with subscription services - usually telecommunications companies. ARPU measures the amount of revenue brought in by a single subscriber per month. Measuring revenues on a per customer, or per unit basis can help to explain how good specific products are at generating revenues. ARPU is also very useful when it can be compared to other user-specific metrics. For instance, subtracting Subscriber Acquisition Cost (SAC) from ARPU over the average period of time a customer stays with the company would yield the gain (or loss) a company gets by attracting each subscriber.