Churn Rate vs Retention: Formulas, Benchmarks & Cohort Curves

What Is Churn Rate?

Churn is the share of customers who leave your product or cancel their subscription during a period. Monthly customer churn is the number of customers lost in the month divided by the number you had at the start of it: a company that starts with 200 customers and loses 10 during the month has 5% monthly churn.

The number looks small, and that's the trap — churn compounds. At 5% a month, and assuming no new customers, you lose roughly 46% of the base over a year. The same math at 2% monthly is about 22% annually. A three-point monthly gap produces two completely different businesses twelve months later.

What Is Retention? How It Differs From Churn

Retention is the other side of the same coin: the share of customers still there at the end of the period. On the customer (logo) side the relationship is simple — retention is 1 minus churn, so 5% churn means 95% retention. On the revenue side that symmetry breaks, and the real information hides there.

Revenue retention can exceed 100%; customer retention never can. Remaining customers upgrade plans, add seats, or buy new modules, and that expansion revenue can more than offset the revenue lost to churn. A company can lose 3% of its customers a month and still grow revenue — one of the strongest signs that the product is deepening inside existing accounts.

A Worked Calculation

Assume you start the month at $50,000 MRR. During the month you lose $3,000 from customers who cancel and $500 from customers who downsize, while gaining $4,000 in expansion revenue from the customers who stayed.

Gross revenue churn counts only the losses: ($3,000 + $500) ÷ $50,000 = 7%. Net revenue churn also counts expansion: ($3,500 − $4,000) ÷ $50,000 = −1%. Negative net churn means the base grows on its own — expressed as net revenue retention, that's 101%.

Report both numbers. A team that watches only NRR can go months without seeing rising small-account churn hidden behind a few large expansions. Gross churn tells you the size of the problem; NRR tells you how strong the compensation is.

What Is a Good Churn Rate?

There is no single right number — billing frequency, segment, and contract length set the range. Still, a practical read for early-stage B2B SaaS: in the SMB segment, monthly logo churn below 2% is healthy and 5% or above signals a structural problem. In annually contracted enterprise, measurement is annual, and below 10% yearly logo churn is considered good.

In B2C and self-serve products the rates are naturally higher; there what matters isn't the absolute number but the trend across cohorts. If each new cohort's retention curve sits above the previous one, the product is moving in the right direction — even while the headline rate stays high.

How to Read a Cohort Retention Curve

An average churn rate hides reality because it compresses customers who arrived at different times into one number. Cohort analysis unpacks it: each month's new customers are tracked as their own group, showing how many are still active in month 1, month 3, and month 6.

The reading rule is simple. If the curve flattens onto a plateau as months pass, you have a core group that pulled the product into their workflow — the most reliable evidence of PMF. If the curve slides toward zero without ever flattening, every customer you win is rented, and growth depends entirely on new arrivals. In some products the curve dips and then ticks back up; that "smile curve" means users return, and the product gets remembered during a specific recurring need.

How Churn Shortens Your Runway

Churn eats growth first and cash second. With 200 customers and 5% monthly churn, you lose 10 customers a month; if sales wins 12, your net growth is 2. Four fifths of your team's effort goes to standing still, the growth chart stalls, and the cost of sales never falls.

The second effect is more insidious: churn makes CAC payback period decisive. At 5% monthly churn, average customer lifetime settles at roughly 20 months. If your CAC payback is 14 months, you see profit from a customer for only 6 of them — which means a small rise in acquisition cost is enough to flip unit economics negative. For most early-stage companies, cutting churn is a cheaper way to extend runway than winning new customers.

Test Churn in the Simulation

In Founder Runway, every turn computes the effect of your decisions on PMF and MRR together. Aggressive sales into the wrong segment lift MRR in the short run; a few turns later PMF Signal falls and revenue growth slows — the in-game equivalent of what you'd experience as churn in real life.

Play a 20-turn run choosing decisions that deepen existing customers, then replay the same scenario focused purely on winning new ones. The runway at the final turn shows clearly which strategy leans less on cash.

Conclusion

Churn isn't one rate but three numbers read together: logo churn shows the scope of the problem, gross revenue churn its financial weight, and NRR how strongly existing customers compensate. Looking at cohorts instead of averages is the only way to see the real retention curve. And because reducing churn is mathematically cheaper than acquiring new customers, when runway tightens the first place to look is the end of the funnel, not the top.