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SaaS Metrics Guide: MRR, ARR, Churn, NRR, and Rule of 40

Understand the core SaaS metrics, how they connect, and the definition choices that make recurring-revenue reporting reliable.

Reviewed 2026-06-18 · 8 minute read · CalcPilot Editorial Team

Short answer

SaaS metrics form a system: MRR and ARR describe recurring revenue scale, churn and NRR describe retention, and the Rule of 40 frames the growth-profitability tradeoff.

Key takeaways

  • Normalize recurring contracts consistently.
  • Reconcile every MRR movement.
  • Separate customer churn from revenue churn.
  • Use NRR and payback to judge growth quality.

MRR and ARR

Monthly recurring revenue normalizes active subscription contracts into one month. Annual contracts are divided by twelve; quarterly contracts by three. Setup fees, hardware, and one-time professional services are normally excluded.

ARR is commonly MRR multiplied by twelve. It is a run rate, not recognized revenue and not a promise that current customers will remain for a year. Keep currency and discount policies consistent.

Churn and retention

Customer churn divides customers lost during a period by customers active at the start. Revenue churn uses recurring revenue instead. Losing one large account can create low customer churn and high revenue churn at the same time.

Cohorts reveal whether retention is improving because they compare customers acquired under similar product and market conditions. Blended churn can hide a weak new segment behind a mature installed base.

Net revenue retention

NRR starts with recurring revenue from the opening customer cohort, adds expansion, subtracts contraction and churn, then divides by starting revenue. New-customer revenue is excluded.

NRR above 100% means existing-customer expansion exceeded losses. It is powerful, but currency, usage revenue, migration, and reactivation policies need written definitions.

Efficiency and balance

CAC payback measures the months of gross profit needed to recover acquisition cost. LTV:CAC compares estimated lifetime economics, while the Rule of 40 adds revenue growth and a chosen profit margin.

No single SaaS metric is a verdict. Review growth, NRR, gross margin, burn, payback, cash runway, and customer concentration together, and preserve a metric dictionary as the company evolves.

Editorial note: This guide explains general formulas and is not financial, tax, legal, or accounting advice. See our calculation methodology.

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