A mentor told me something years ago that I keep coming back to: you don't take a percentage to the bank. He was talking about product margins at the time, but it applies to almost everything in marketing — and it's a blind spot that costs CMOs credibility every single year.
We love ratios. LTV:CAC. ROAS. Conversion rate. Efficiency scores. They're clean, they compress complexity into a single number, and they're easy to benchmark. The problem is that ratios alone don't tell you how the business is doing. They tell you how efficiently it's doing it — and there's a large gap between those two things.
What Ratios Hide
A 3:1 LTV:CAC is a very different business outcome when you've invested $10 million versus $50,000. Scale matters. Timing matters. A 2:1 ratio within 12 months with $100,000 invested is not the same business as a 2:1 ratio with $1 million invested — the absolute contribution is ten times larger in the second case, even though the ratio is identical. When you present only the ratio, you're hiding the most important variable: how much growth the engine is actually generating.
Similarly, an improving ROAS can mask a declining absolute revenue contribution if the channel mix is shifting toward lower-spend, lower-LTV customers. Ratios can move in the right direction while the underlying business math deteriorates. The CFO usually sees this. The CMO presenting only ratios often doesn't — and that gap in perception is where marketing loses its seat at the table.
The Language That Earns the Seat
The CFO doesn't care that your ratio improved. What they care about is how many dollars hit the account and when — and whether the marketing engine is creating customers who pay back their acquisition cost before the company needs to refinance. The best CMOs I've worked with speak in absolutes:
- "We added $1.2M in net new revenue this quarter, with a contribution margin of 48%."
- "CAC payback is under eight months — we're funding growth from operations, not from burn."
- "Contribution margin per customer is up $40 year over year — every new customer is worth more than last year's cohort."
These statements don't just tell the CFO that things are working — they tell them why, in terms that map directly to the P&L and the cash flow statement. That's how marketing stops being treated as a cost center and starts being treated as a capital allocation decision.
The Practical Fix
The fix isn't to stop tracking ratios. It's to always pair them with the absolute underneath. Every time you report LTV:CAC, also report LTV minus CAC — the actual dollar value created per customer. Every time you show ROAS, also show the absolute revenue and contribution margin the channel drove in dollars.
Ratios are how you run diagnostics. Dollars are how you make decisions. Know the difference — and make sure the people you report to know which one you're showing them.
David Manela is co-founder of Exactius, a growth and data science company. Follow him on LinkedIn for more frameworks on growth, marketing, and capital allocation.
David Manela
David Manela is the founder of Exactius and creator of the Growth Operating System — a framework for deploying capital-efficient, compounding growth inside scaling companies.
FAQ
Frequently asked
Which metrics should I pair with CAC to measure marketing efficiency?
Pair it with metrics that show value, time and scale. The article recommends reporting LTV minus CAC, the dollar value created per customer, next to the LTV:CAC ratio, and absolute revenue and contribution margin next to ROAS. Add CAC payback, which investor David Skok's SaaS definitions calculate as CAC divided by monthly revenue per account times gross margin, and total dollars invested so scale is visible.
What is the difference between ROAS and contribution margin?
ROAS is conversion value divided by ad spend. Google's Target ROAS documentation illustrates it as $5 in sales for $1 in ad spend, a 500 percent ROAS. It ignores product costs, shipping, discounts and returns. Contribution margin subtracts those variable costs from revenue, so it shows what is left to cover fixed costs and profit. A campaign can show a high ROAS and still lose money on each order.
What is a good CAC payback period?
David Skok's original guideline for SaaS was 12 months or less, and he wrote that many of the best SaaS businesses recover CAC in 5 to 7 months. His updated notes say payback under 12 months is very rare in practice, and that around 20 months can work for enterprise businesses with a land and expand model. These figures come from SaaS. Ecommerce and other models should set targets from cash position and repurchase timing.
How is CAC calculated?
Skok's SaaS definition divides total sales and marketing expenses for a period by the number of new customers acquired in that period. Two choices change the answer. One is whether costs are fully loaded, including salaries, tools and partner fees, or limited to paid media. The other is whether CAC is blended across all new customers or limited to those from paid channels. State which version you report.
Is a 3:1 LTV:CAC ratio good?
As a ratio, it meets investor David Skok's SaaS guideline that LTV must be at least three times CAC. The article's point is that the same 3:1 can describe very different businesses. At $50,000 of acquisition spend and at $10 million, the dollars created differ by a factor of 200. Report the ratio together with the absolute dollar value it represents and the time it takes to pay back.
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