LTV:CAC Ratio
LTV:CAC ratio is the relationship between how much value a customer delivers across their lifetime (LTV) and how much it cost to acquire them (CAC). It's the single most-cited health metric for subscription and SaaS businesses — a rough shorthand for "is your growth engine profitable?"
LTV:CAC ratio is the relationship between how much value a customer delivers across their lifetime (LTV) and how much it cost to acquire them (CAC). It's the single most-cited health metric for subscription and SaaS businesses — a rough shorthand for "is your growth engine profitable?"
Why It Matters
You can hit growth targets that bankrupt you. Spending $1,000 to acquire a customer worth $800 over their lifetime feels like growth on a top-line chart and kills cash runway. LTV:CAC makes that math inescapable. Bessemer's State of the Cloud, OpenView's SaaS benchmarks, and nearly every Series A deck use LTV:CAC as a primary diligence metric. For inbound marketing, it's also the scoreboard: content and SEO typically produce lower-CAC customers than paid ads, so a rising LTV:CAC ratio often reflects a shift from paid to organic.
The Formulas
LTV (simple SaaS):
LTV = (ARPU × Gross Margin) / Monthly Churn Rate
Where ARPU is average revenue per user per month, gross margin is the fraction of revenue left after COGS, and monthly churn is the % of customers lost each month.
CAC:
CAC = Total Sales + Marketing Spend / New Customers Acquired
Include everything — ad spend, salaries, tools, commissions, content production. Naked "ad spend only" CAC is almost always wrong.
Ratio:
LTV:CAC = LTV / CAC
The 3:1 Rule
The industry rule of thumb — first proposed by Bill Gurley and David Skok — is:
- < 1:1: Burning money on every customer. Not viable.
- 1:1 to 3:1: Break-even or thin profit. Growth is subsidized by investment; needs discipline.
- 3:1: Healthy SaaS. Most venture-backed companies target this.
- > 5:1: Probably under-investing in growth. You could spend more on acquisition and still win.
3:1 reflects a sensible cushion — each customer returns three times their acquisition cost over their life, leaving room for salaries, product, ops, and margin.
CAC Payback Period — The Underrated Sibling
LTV:CAC is useful but lies to you in two ways: it assumes LTV is accurately forecast (it's usually not), and it ignores time. A customer worth $10,000 over 10 years is worse than one worth $3,000 in year one if you're cash-constrained.
CAC payback period = months until the customer's contribution margin recoups CAC.
Good payback: under 12 months for SMB SaaS, under 18 months for mid-market, under 24 months for enterprise. Teams with cash constraints should lead with payback and use LTV:CAC as a secondary check.
How to Improve LTV:CAC
Lower CAC:
- Shift budget from paid to inbound (content, SEO, community, product-led)
- Improve free-trial-to-paid conversion
- Tighter ICP targeting so fewer wasted spend on wrong-fit leads
- Stronger referral loop
Raise LTV:
- Reduce churn (usually higher ROI than raising price)
- Expansion revenue — upsells, cross-sells, seat growth
- Annual plans instead of monthly
- Move upmarket to higher ACV segments
Both at once (highest leverage):
- Fix activation. Better activation reduces early churn AND makes acquisition more efficient because activated users refer others.
Common Mistakes
Excluding salaries from CAC: Makes CAC look healthier than it is. Fully loaded CAC is the honest number.
Assuming flat LTV forever: LTV is a forecast. If your churn rate just jumped 30%, past LTV calculations are fiction.
Optimizing only LTV:CAC: A great ratio with a 5-year payback period still kills cash-constrained startups.
Mixing channels: A blended CAC hides that paid is catastrophic and inbound is magical. Segment by channel.
Not adjusting for gross margin: A 30%-margin business and a 90%-margin business with the same revenue have wildly different LTVs.
Cohort vs blended: Company-wide numbers hide cohort trends. Always calculate LTV:CAC by acquisition cohort over time.
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