Monthly recurring revenue, or MRR, is the centerpiece of most subscription-based businesses. It represents the predictable subscription income a company earns, normalized into a monthly figure so that growth can be tracked in a single, consistent unit. Because contracts of different lengths are flattened into the same monthly lens, MRR becomes the yardstick against which expansion, contraction, and loss are measured. When MRR is rising, founders generally feel good about the business; when it is flat or falling, something is wrong underneath.
Standing against MRR is churn, the rate at which customers or revenue are lost over a period. Even a company with strong acquisition can find that its growth is erased each month by subscribers leaving, so churn is the silent counterweight to every marketing win. The danger is that churn is easy to overlook when headline signups look impressive, which is why it deserves explicit measurement and a target of its own.
Retention is usually examined at two levels. Gross revenue retention measures how much existing revenue is protected before any expansion is layered on; it shows the baseline survival of the customer base. Net revenue retention, often called NRR, takes that same starting revenue and adjusts for expansion, contraction, and churn. When NRR exceeds 100%, existing accounts are collectively growing, which can make a SaaS business very efficient. A common mistake is to look only at NRR and overlook what gross retention reveals about core churn problems, so the two numbers should always be read together. Expansion revenue, which comes from existing customers upgrading, adding seats, or buying add-ons, is what pushes NRR above the gross figure, but it depends on a healthy customer success motion after the initial sale. Treating expansion as automatic, rather than as something earned, is a frequent pitfall.