Скачать или смотреть The Big Assumption You’re Overlooking in Your CAC | SaaS Metrics School | CAC

Welcome to another edition of SaaS Metrics School with Ben Murray, The SaaS CFO! Today, we’re diving into a critical assumption that many SaaS operators and finance teams overlook when calculating Customer Acquisition Cost (CAC)—and it can have major implications on your SaaS business.

Before we dive into today’s topic, let’s meet in person! I’ll be attending Nathan Latka’s SaaS Open in New York City in early September, followed by SaaStr in San Francisco, where I’ll also be speaking at the first-ever SaaStr CFO Summit. These are incredible events for SaaS operators, founders, and CFOs. Hope to see you there!

The Hidden Assumption in Your CAC Calculation

CAC is a fundamental SaaS metric used to measure the cost of acquiring new customers. On the surface, it seems straightforward, but lurking in your spreadsheets is a big assumption that can completely change your CAC analysis.

1. Two Forms of CAC: Gross CAC vs. Unit Cost CAC

Gross CAC: This is the total amount spent on customer acquisition and is derived directly from your SaaS P&L under sales and marketing expenses.

Unit Cost CAC: This measures the cost to acquire a single customer, user, or account and is what most people think of when discussing CAC.

For early-stage SaaS companies with a single product line and no expansion potential, 100% of sales and marketing spend is typically dedicated to acquiring new customers. In that case, it’s fine to allocate the full amount to CAC calculations.

However, as your company scales and adds new products, upsell, and cross-sell opportunities, your sales and marketing efforts are no longer focused solely on new customers. This is where the big assumption comes in.

2. The Assumption That Can Skew Your CAC Metrics

As your business grows, your sales and marketing expenses become commingled—some go towards acquiring new customers, while others are focused on expansion revenue from existing customers. If you blindly allocate all sales and marketing expenses to new customer acquisition, your CAC will be overstated and inaccurate.

To correct this:

Sales Allocation: Split sales team costs between new and existing customer acquisition.

Marketing Allocation: Identify what portion of marketing spend is dedicated to acquiring new customers versus expanding existing accounts.

Perform Monthly Adjustments: Once you’re above $10M ARR, regularly update this allocation every month to maintain accuracy.

3. Why This Matters for Your SaaS Business

Your CAC Payback, LTV:CAC, and cost of ARR depend on accurate CAC calculations.

Investors and board members analyze these numbers closely. Misallocation can create red flags in due diligence or investor conversations.

It impacts SaaS financial planning and forecasting—especially as you scale beyond $10M ARR.

As part of my Five-Pillar SaaS Metrics Framework, this falls under Pillar 5: Efficiency, which is a key area SaaS companies need to optimize as they scale.

Join My Upcoming SaaS Metrics Course

Want to go deeper into CAC and SaaS financial modeling? I’ll be teaching my Five-Pillar SaaS Metrics Framework course in September! Check out my SaaS Academy for more details:

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