MRR Churn Math Every SaaS Founder Must Know

The Core MRR Equation

Every month, your MRR moves by a simple equation: New MRR = Starting MRR + New + Expansion − Churned − Contracted. Growth feels like a function of sales, but churn is the silent term that compounds against you. Model it with our MRR Growth Projector to see the curve.

Why Small Churn Differences Are Enormous

At 2% monthly logo churn, the average customer lasts 50 months. At 5%, they last 20 months. That 3-point gap more than halves customer lifetime value — and therefore halves what you can afford to spend on acquisition. Churn is leverage in reverse.

Worked example: $50k MRR, 8% monthly growth from new sales, 4% monthly churn. Net growth is roughly 4% — but you are re-selling nearly half your new revenue every month just to stand still. Cut churn to 2% and net growth doubles without a single extra sale.

Logo Churn vs Revenue Churn

Logo churn counts customers lost; revenue churn counts dollars lost. They diverge when expansion revenue exists: you can lose 3% of logos monthly yet grow revenue if remaining accounts expand. Best-in-class SaaS companies run negative net revenue churn — the installed base grows on its own.

• Track both monthly; report net revenue retention to investors.
• Segment churn by cohort, plan tier, and acquisition channel.
• Attack early-life churn first — the first 90 days dominate lifetime churn.

Connecting Churn to Valuation

Revenue multiples expand as net retention rises because predictable, compounding revenue is worth more. A company at 120% net retention can command a meaningfully higher multiple than an identical-revenue peer at 95%. Sanity-check the output with our Startup Valuation Calculator and our Churn Rate Calculator.

Worked Example: The Same Cohort at 2% vs 5% Churn

Take a starting cohort of 100 customers and apply monthly logo churn for a year. Customers remaining = 100 × (1 − churn)¹²:

Monthly churn	Left after 6 mo	Left after 12 mo	Avg. lifetime
2%	~89	~78	50 months
5%	~74	~54	20 months
10%	~53	~28	10 months

The 5% company keeps 24 fewer customers from the identical starting cohort — nearly a quarter of the base gone — and each customer is worth less than half as much over their lifetime. That "small" 3-point gap is actually a 2.5x difference in customer lifetime value, which is why investors weight net revenue retention so heavily.

Gross vs Net Revenue Churn

Gross revenue churn measures dollars lost to cancellations and downgrades, ignoring expansion. Net revenue churn subtracts expansion and upsell dollars from that loss. A company can post 4% gross churn and −2% net churn at the same time — losing some accounts while the remaining base spends more. Track gross churn to diagnose product-market fit problems; track net churn to forecast the business. Model your own numbers with our Churn Rate Calculator.

Bottom Line

Growth gets the headlines; churn decides the outcome. Run your numbers in the MRR Growth Projector, then put one initiative per quarter against your biggest churn segment.