Customer Acquisition Cost (CAC) is one of the most talked-about metrics in ecommerce, but it's also one of the most misunderstood. It’s not just an expense to be minimized. Instead, you should think of it as an investment lever for growth. The "cost" to acquire a customer is only half the story. The other half is what that customer is worth to you over time. Once you connect those two ideas, you can use CAC to strategically scale your business.
So, what's a 'good' CAC?
A "good" CAC is always relative to your Customer Lifetime Value (LTV). There is no universal number that works for every business. As Nik Sharma and Moiz Ali often stress on Limited Supply, managing this ratio is fundamental to your brand's sustainability. If your LTV is $100, a $40 CAC is great. If your LTV is $30, a $40 CAC will put you out of business very quickly. The goal isn’t just to lower your CAC, it's to maintain a healthy margin between what you spend to get a customer and what that customer spends with you over their lifetime.
Many brands, especially early on, make the mistake of looking at CAC in isolation. They might pause a campaign because the upfront cost per order seems too high, without realizing those customers have a high repeat purchase rate and are actually very profitable in the long run. The key is shifting your mindset from "How much did this customer cost me today?" to "How much profit will this customer generate for me over the next 12-24 months?"
How does Lifetime Value (LTV) change the CAC calculation?
Understanding LTV completely changes how you can approach growth. As Taylor Holiday explained on an episode of Ecommerce Conversations, most brands operate on a "first sale gross margin" model. This means their CAC has to be profitable on the very first transaction. If they make $25 in gross profit on an order, their CAC must be less than $25. This severely limits how much you can spend on ads and caps your ability to scale.
The more advanced model is to use LTV to inform your allowable CAC. If you know that a customer acquired through a specific channel will spend, on average, three times with you over two years, you can afford to spend much more to acquire them upfront. You might even be willing to lose money on that first sale, confident you'll become profitable on the second or third purchase. This LTV-based approach is what unlocks more expensive, and often larger, marketing channels that your competitors, stuck in a first-sale profitability mindset, can't touch.
Can my CAC actually be negative?
Yes, and it's the holy grail of acquisition marketing. Taylor Holiday laid out this very idea of how to achieve negative CAC. It doesn’t mean you’re getting customers for free. It means a new customer’s first purchase generates more immediate profit than what you spent to acquire them. In this scenario, your marketing doesn't just pay for itself, it generates positive cash flow from day one.
This is rare, but it can happen with high-AOV products or when a customer buys multiple items in their first order. For example, if you spend $50 to acquire a customer, and they place a $300 order with a $70 profit margin, you’ve achieved a "$20 negative CAC." You’ve instantly made back your ad spend plus an extra $20. This allows you to reinvest in marketing even more aggressively, creating a powerful growth flywheel.
How do different channels affect my CAC?
Your CAC will, and should, be different across every marketing channel. Thinking in terms of a single "blended CAC" can hide major problems and opportunities. As Rory McGonigle discussed on the Ecommerce Exits Podcast, the cost of acquiring customers off-Amazon is very different from sponsored ads within the marketplace. Similarly, your CAC on a mature channel like Google Search will likely be different from a newer, awareness-focused channel like TikTok.
On The My Wife Quit Her Job Podcast, Mike Jackness and Dave Bryant highlighted how platform advertising costs are a huge variable. What works on Facebook may not work on Amazon. The key is to track your CAC on a per-channel basis. This allows you to see which channels are bringing in your most valuable customers (i.e., those with the highest LTV) and adjust your spending accordingly. You might find that a high-CAC channel is actually your most profitable one because it delivers customers who stick around the longest.
Ultimately, using CAC effectively is about moving from simple expense tracking to a more sophisticated, portfolio-style management of your customer base. When you pair CAC with LTV and segment by channel, you get a clear picture of where to invest your marketing dollars for sustainable, long-term growth. It’s the difference between just keeping the lights on and building a truly valuable brand.