The percentage of subscribers who cancel in a given period, usually monthly. Churn decides whether a subscription business compounds or leaks: it sets your effective LTV, which sets your allowable CAC, which sets how hard you can compete for customers. Two traps: benchmarking against a universal target when honest churn varies sharply by subscription model, and ignoring involuntary churn - payment failures cause 20-40% of all subscription churn, and that customer never decided to leave. Card retries and dunning flows are the most fixable retention work you will ever do, and wrong delivery frequency is the biggest single driver of the voluntary kind.
Benchmark. Replenishment subscriptions typically run 5-8% monthly, supplements 7-10%, curation or discovery boxes 10-15%+. Treat 5-10% as a blended starting range, not a target: top-quartile brands run a few points under typical, and cutting 2-3 points dramatically changes the economics.