The formulas every buyer should know — monthly churn, annual churn, NRR, logo retention, and churn-adjusted MRR. Plus the fastest way to compute them: upload a CSV to ChurnLens.
Every SaaS buyer needs to know how to calculate churn from raw data — because the seller's number is never the real number. This page gives you the exact formulas: monthly logo churn, revenue churn, annual churn, NRR, GRR, and churn-adjusted MRR. Run them on any subscription CSV and you'll know in 10 minutes whether the deal is worth pursuing. Then upload to ChurnLens to get every metric automatically.
Six churn formulas every buyer must know: monthly logo churn (customers lost / starting customers), revenue churn (MRR lost / starting MRR), annual churn (1 - (1-monthly)¹²), NRR (including expansion), GRR (excluding expansion), and churn-adjusted MRR (MRR × (1-churn rate)¹²). ChurnLens computes all six automatically from any CSV upload.
Here's a real-world walkthrough using the formulas above.
Jan 2026 snapshot:
Results:
Manual churn calculation is prone to six classes of errors that systematically favor the seller:
ChurnLens handles all six automatically from a raw CSV. No formulas to maintain, no spreadsheets to break.
Upload a subscription CSV and get all churn metrics computed automatically: logo churn, revenue churn, NRR, annualized rates, and the churn-adjusted MRR projection.
Upload & Calculate →Sellers hide churn in 7 ways. Most buyers catch 0. Get the full checklist + a sample report on a real $48K MRR case study.
Get the free checklist →Get the 23-point buyer-side churn audit checklist and see exactly what to demand from any seller's subscription data.
Want to automate this analysis? Get the 23-point churn audit checklist →Hidden churn is revenue decay that headline metrics conceal: customers on annual plans who have already stopped using the product, paid accounts sitting inactive, or revenue concentrated in a few logos about to leave. A SaaS business can show flat MRR while its real retention is collapsing. ChurnLens surfaces these signals before you buy, so you price the deal on true revenue quality.
ChurnLens analyzes five dimensions: revenue concentration, logo retention, annual-plan churn risk, inactive paid accounts, and MRR decline patterns. Each is weighted into a single 0-100 revenue-quality score benchmarked against comparable SaaS businesses. The score tells an acquirer whether reported MRR is durable or propped up by customers who are one renewal away from leaving, all before the deal closes.
Purchase price is usually a multiple of recurring revenue, so overstated retention directly inflates what you pay. A business with 20% hidden annual-plan churn is worth far less than its MRR implies. Buyers who skip churn diligence discover the decay only after closing, when it is too late to renegotiate. ChurnLens gives that visibility during the evaluation window instead.
Watch for revenue concentrated in a handful of accounts, a widening gap between signups and active users, annual contracts that never renew, and MRR that grows only through discounting. Each pattern signals fragile revenue. ChurnLens automatically flags these red flags from uploaded revenue data and ranks them by how much they threaten the durability of the recurring revenue base.
| Risk dimensions scored | 5 |
|---|---|
| Revenue-quality score range | 0-100 |
| Built for | Acquirers, PE, founders |
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