TL;DR: Healthy B2B SaaS unit economics mean an LTV/CAC ratio above 3:1 and payback period under 12 months. This guide walks through calculating CAC, LTV, and payback period with real formulas, benchmarks, and examples from companies at €100K-€5M ARR.
You’ve been selling. Customers are signing. Revenue is growing. Life is good. Then someone asks: “What’s your CAC?” And you realize you have no idea.
Most early-stage founders fall into this trap. You’re focused on closing deals and building product. Unit economics feel like something you’ll worry about later.
Here’s the problem: you’re flying blind. Unit economics tell you whether your business is actually working. Not whether you’re growing. Whether it’s actually working.
What Is CAC (Customer Acquisition Cost)?
CAC is simple: how much money did you spend to acquire a customer?
CAC = Total Sales & Marketing Spend / Number of New Customers Acquired
Include salaries for sales people, marketing tools and ads, sales tools, your own time spent selling, and commissions. Most early-stage founders underestimate their CAC because they don’t count their own time.
What Is LTV (Lifetime Value)?
LTV = (ARPU x Gross Margin) / Monthly Churn Rate
ARPU is average revenue per user per month. Gross Margin is the percentage of revenue that’s profit after direct costs. Monthly Churn Rate is the percentage of customers lost each month.
Example: $500 ARPU, 80% margin ($400), 10% churn = $4,000 LTV. If your CAC is $5,000, you’re losing money on every customer.
The benchmark for a sustainable B2B SaaS business. Below 1.5 means you're bleeding money on acquisition.
Under 12 months is healthy. Below 9 is excellent. Above 15 is a warning sign.
Most B2B SaaS targets 70–85% gross margin. This is the multiplier in your LTV formula.
The Magic Ratio: CAC vs. LTV
The rule of thumb for SaaS: LTV/CAC below 1.0 means you’re losing money. 1.5-2.0 is early-stage typical. 3.0+ is the target for a sustainable business.
The fix often comes from two places: increasing prices (raising LTV) and being more selective about prospects (reducing CAC). Check out our guide on pricing your B2B SaaS to maximize revenue.
Understanding Payback Period
Payback Period = CAC / (ARPU x Gross Margin)
For early-stage SaaS, 9-15 months is reasonable. Below 9 months is great. Above 15 months is a warning sign that means you can’t afford customer churn.
How to Actually Use These Numbers
If CAC is too high, look at acquisition channels. Double down on lowest-cost channels. If LTV is too low, you have a pricing or retention problem. If payback period is too long, focus on onboarding and reducing churn.
Track these monthly. Set up your CRM to track acquisition date, MRR per customer, churn date, and direct costs. See our guide on CRM setup for early-stage SaaS.
The Real Conversation
Unit economics aren’t sexy. But they’re the foundation of everything. You can have 10x growth and a failing business. The only way to know which you are is to look at the numbers.
To discover which tools can help you track and optimize these metrics automatically, check out our guide to the best AI sales tools for SaaS.
If you’re not sure whether your unit economics are healthy, this is exactly the kind of thing a revenue operations consultant untangles — and you can book a free audit with us. We’ll look at your CAC, LTV, and payback period and give you specific recommendations.
Want this run on your pipeline?
€500, 90 minutes. Credited against any Build.
Wouter van de Velde
10+ years as a B2B sales operator. €4M+ generated in revenue. Now builds sales systems for Dutch and EU SaaS founders who'd rather be shipping product.
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