What is churn and how much churn is too much?

The short answer

Churn is the rate customers leave, and it silently caps your growth because you're refilling a leaky bucket. For SMB SaaS, ~3-5% monthly is common but painful; for B2B you want low single digits annually. If your product has high churn, fixing retention beats pouring money into acquisition every single time.

Go deeper, your way

2 hand-picked resources, 1 link-checked. Pick how you want to dig in.

📄 Article

✓ Link checked Free Intermediate

Why we picked it The reference primer on the metrics and market-sizing logic investors use, including bottom-up market sizing that keeps founders honest about how big a market really is. Canonical a16z source.

16 Startup Metrics

From a16z by Andreessen Horowitz (a16z) ~15 min read

Size markets bottom-up from customer count and willingness to pay
Know the metrics that actually signal a healthy business
Distinguish real traction from vanity metrics
Use consistent definitions when comparing yourself to the market

Open a16z.com →

📄 Article

Free Advanced

Why we picked it David Sacks (PayPal, Yammer, Craft Ventures) distills the metrics that actually predict a SaaS company's health, including the burn multiple he popularized. Sharp, operator-grade, and opinionated.

The SaaS Metrics That Matter

From sacks.substack.com by David Sacks essay

Net revenue retention and the burn multiple reveal true capital efficiency
Focus on a small set of metrics reviewed on a strict weekly cadence
Growth and profitability must be balanced (the Rule of 40)

Open sacks.substack.com →

Terms in this answer

Retention Churn

People also ask

What are unit economics and why do they matter? Unit economics is the profit or loss on a single customer or unit, strip away the noise and ask 'do I make money on one customer?' If the answer is... Beginner 3 resources → How do I calculate CAC (customer acquisition cost) and LTV? CAC = total sales and marketing spend divided by new customers acquired in that period, count everything, not just ad spend. LTV = the profit (not ... Intermediate 3 resources → What is a good LTV to CAC ratio? The rule of thumb is LTV:CAC of at least 3:1, earn back roughly three times what it costs to acquire a customer. Below 1:1 you lose money on every ... Intermediate 3 resources → What metrics should I actually track as an early-stage SaaS founder? Early on, obsess over MRR growth, churn, gross margin, and CAC payback, ignore vanity metrics like downloads and pageviews. Net revenue retention t... Intermediate 3 resources → How do I build a simple financial model or revenue projection? Build bottom-up from real drivers, leads, conversion rate, price, churn, not top-down from 'we'll grab 1% of a huge market.' A useful early model f... Intermediate 3 resources → My CAC looks great but I paid for it with a founder-led discount. How do I know my unit economics without the promo? Discounts and founder hustle hide your real acquisition cost, so run two versions: the promo number and the number when a stranger buys at list pri... Intermediate 2 resources →

Also in D2C

The same ground, over in Money, pricing & unit economics, our D2C track.

I'm not a finance person, what books/records do I actually need to keep from day one? At minimum: a sales register (every order, with GST split if applicable), a purchase/expense register (raw materials, ads, shipping, software), a b... 3 resources → What is cohort analysis, and why does it matter more than a single repeat-rate number? Cohort analysis groups customers by when they first bought and tracks how each group behaves over time - so instead of one blended '35% repeat rate... 3 resources →

Also in How Founders Use AI

How founders actually use AI for this, over in Finance & Accounting.

How do founders use AI for bookkeeping, invoicing, runway and burn analysis? Founders now hand AI the boring parts of finance: reading supplier invoices from email, categorizing bank transactions, drafting collection emails ... 4 resources → Why build financial models with AI instead of from a blank spreadsheet? Because the AI already knows the structure, how an income statement links to a balance sheet and cash flow, what assumptions a SaaS or D2C model ne... 4 resources →

eChai Partner Brands