Monthly Recurring Revenue (MRR) is the total predictable revenue a business expects to receive on a monthly basis from its subscription customers. MRR is a critical metric for subscription-based businesses as it helps measure the stability and growth of revenue over time. It only includes recurring revenue, such as monthly subscription fees, and excludes one-time payments, setup fees, or any other non-recurring charges.

MRR is calculated by multiplying the total number of subscribers by the average revenue per user (ARPU) per month.

1. Basic Example: A company has 100 subscribers, each paying $50 per month. The MRR is:
\begin{align}MRR&=100\times50\cr&=5,000\text{ USD}\end{align}

2. Tiered Pricing Example: A company offers two subscription tiers: 50 subscribers pay $30 per month, and 50 subscribers pay $70 per month. The MRR is:
\begin{align}MRR &=(50 \times 30)+(50 \times 70)\cr&=1,500+3,500\cr&=5,000\text{ USD}\end{align}