MRR is a metric suited best for subscription-based business models. Together with metrics that track customer acquisition and churn, it gives a good forecast of expected future revenues.
The same metric can also be calculated on an annual basis (Annual Recurring Revenue). This can make sense, for example, when the minimum subscription period is one year.
The Monthly Recurring Revenue is calculated by adding up all recurring revenue streams.
Σ recurring revenue
A company gets €50 revenue each from 200 users and €100 from 20 premium users per month.
(50€ x 200) = 10,000€
+ (100€ x 20) = 2,000€