Unit Economics for B2B SaaS Founders Who Aren't Finance People

If you have been through more than a few investor conversations, you have almost certainly been asked about your unit economics. If you found yourself winging it, or giving numbers you were not entirely confident in, this article is for you.

Unit economics is one of those phrases that sounds more complicated than it is. At its core, it answers a simple question: for every customer you acquire, how much money do you make versus how much it cost you to get them? The answer to that question tells you more about the health of your business than almost any other metric.

The four metrics you need to know

1. Customer Acquisition Cost (CAC)

CAC is the total cost of acquiring one new paying customer. The formula is:

CAC = Total sales and marketing spend / Number of new customers acquired in the same period

What to include in the numerator: salaries and commissions for your sales and marketing team, paid advertising spend, events and sponsorships, any tools used specifically for sales and marketing purposes such as CRM software or marketing automation. What not to include: product development costs, customer success costs after the customer is acquired, general and administrative costs.

A common mistake is to use only the direct marketing spend and exclude the cost of the people doing the selling. This produces a CAC that looks better than reality. Include all fully-loaded costs of acquiring customers.

2. Lifetime Value (LTV)

LTV is the total revenue you expect to receive from a customer over the entire time they remain a customer. The most common formula for SaaS businesses is:

LTV = Average Revenue Per Account (ARPA) / Monthly Churn Rate

Note that this is a simplified calculation. A more precise LTV calculation accounts for gross margin: (ARPA x Gross Margin) / Churn Rate.

3. LTV:CAC Ratio

The LTV:CAC ratio tells you how much value you are generating per dollar spent acquiring customers.

LTV:CAC = LTV / CAC

For B2B SaaS, the benchmarks investors typically reference at seed stage are: LTV:CAC above 3x is the minimum to demonstrate a viable business. Above 5x is strong. Below 2x requires either a growth story that justifies near-term losses or a credible path to improving the ratio.

4. CAC Payback Period

CAC payback period is the number of months it takes for a customer to generate enough revenue to cover the cost of acquiring them.

CAC Payback = CAC / Monthly ARPA

Payback under 18 months is the typical benchmark. Payback under 12 months is strong. Payback over 24 months will require a clear explanation.

Unit economics do not need to be perfect at seed stage. They need to be moving in the right direction, and you need to understand what levers control them.

What investors actually do with these numbers

When an investor sees your unit economics, they are doing three things. First, they are checking whether the numbers are internally consistent. Second, they are comparing your numbers to the benchmarks they see across their portfolio. Third, they are assessing whether you understand the levers that drive these metrics.

How to improve your unit economics

Improving LTV

The most direct path to improving LTV is reducing churn. The second path is increasing ARPA through upsells, tier upgrades, or seat expansion. Net Revenue Retention above 100 percent is one of the most powerful metrics you can show an investor.

Reducing CAC

CAC reduction is almost always about improving either the efficiency of your marketing spend or the efficiency of your sales process. Track each stage of your funnel separately. The stage with the worst conversion rate is where to focus. Throwing more spend at the top of a leaky funnel does not reduce CAC. Fixing the leak does.

Ready to apply this to your business? Get early access to YourCFO at yourcfo.tech.