Retention decides whether growth compounds or leaks. A business adding 10% new revenue a month while losing 8% to churn is working extremely hard to stand still, and no amount of acquisition spend fixes a product people leave. These calculators quantify what leaving actually costs.
Which one you want
LTV & CAC is the headline pair: what a customer is worth over the relationship, against what it cost to win them. A ratio above 3:1 is the conventional healthy floor, but read it with CAC Payback — a 3:1 ratio that takes 30 months to repay is a cash-flow problem regardless of how good the multiple looks. NRR captures expansion as well as loss and is the single number late-stage investors care most about; above 100% means the existing base grows on its own. Use Churn Impact and Churn Revenue Loss to convert a percentage into the dollars it removes from a plan, and Churn Cohort to see whether retention is genuinely improving or whether one good cohort is flattering the average.
What the numbers mean
Churn is deceptive at small percentages. Monthly churn of 5% sounds survivable and implies an average customer lifetime of 20 months; 2% implies 50 months, and roughly two and a half times the lifetime value from the same acquisition spend. Always separate logo churn from revenue churn — losing many small accounts and losing one enterprise contract produce very different percentages and require very different responses.