OR(Lost MRR / Start MRR) %` | Measures leakage; high churn kills growth. Revenue churn shows $ impact. | SaaS: <1-2% monthly (Logo), <1% (Net Revenue Churn ideally) | | ARPU / ARPPU | Average Revenue Per User / Per Paying User = MRR /(ARPU * Gross Margin %) / Customer Churn Rate | Predicts total profit from an average customer. | LTV > 3x CAC | | Customer Acquisition Cost (CAC) | Total Sales & Marketing Spend /CAC / (ARPU * Gross Margin %) (in months) | Time to recoup acquisition cost. | SaaS: < 12 months ideally. | | Expansion MRR Rate | (Expansion MRR from existing cust.) / Starting MRR % | Measures growth from upsells/cross-sells from existing base. Powerful growth lever. | >10-30% depending on stage. | | Net Revenue Retention (NRR) | (Start MRR + Expansion - Downgrade - Churn) / Start MRR % | The holy grail. Measures $ growth from existing cohort. >100% = negative churn. | >100% (Good), >110% (Great), >120% (Elite) | ---