Average Revenue Per User or Unit (ARPU) is the revenue generated per user or unit within a time period, usually monthly or yearly.
# of Users or Units
In January, you report revenue of $500,000 with 10,000 users. Your monthly ARPU is $50 ($500,000 revenue ÷ 10,000 users).
You introduce new add-ons at the end of the year that your customers purchased. Therefore, you report annual revenue of $750,000 with 10,000 users for the year. Your yearly ARPU is $75 ($750,000 revenue ÷ 10,000 users).