CAC Calculator

Divide everything you spent winning customers by the number of new customers that spending produced, over the same period: CAC = spend ÷ new customers. Spend $10,000 in a quarter and sign 50 new customers and your CAC is $200. Two words in that sentence do the real work. New excludes renewals, repeat orders and upsells to people you already had — those cost far less to win and folding them in makes CAC look artificially cheap. Same period matters because acquisition has a lag: money spent in the last week of a quarter often lands as customers in the next one, which is why CAC computed monthly bounces around and CAC computed quarterly usually behaves. The output is an average, and averages hide a lot. It is worth recalculating per channel, per segment, and per product line, because a single blended figure can be entirely composed of one cheap source subsidizing several expensive ones.

The most common way CAC gets understated is by counting only the media invoice. The denominator counts every customer; the numerator has to count every dollar that went into getting them. That means salaries and payroll taxes for the sales and marketing team, not just their ad budgets. In any business with human selling, compensation is usually the largest line by a wide margin, and leaving it out can halve the reported CAC. It also means sales commissions, the software the funnel runs on (CRM, email platform, analytics, call tooling), creative and content production, agency retainers, event and travel costs, and free trials or onboarding you give away to close the deal. What does not belong: product development, customer support for existing accounts, and general overhead like accounting or office rent. Those are real costs, but they are not acquisition, and pushing them in makes the metric useless for the decision it exists to inform — whether spending more to grow is worth it. One honest test: if you stopped acquiring customers tomorrow, which of these costs would go away? Those are the ones that belong in CAC.

A $200 CAC is neither good nor bad on its own. It is good if a customer is worth $1,000 to you and catastrophic if they are worth $150. The comparison metric is LTV, and the number people watch is the LTV/CAC ratio. The widely used rule of thumb is 3 or above. The logic behind it is not mystical: LTV is normally measured in gross profit, and that gross profit still has to cover product development, support, general overhead and eventually actual profit. A ratio of 1 means you break even on the customer and fund nothing else. A ratio of 2 leaves thin cover. Around 3, the business generally has enough left over to run itself and grow. The ceiling is less obvious but just as real. A ratio of 8 or 10 usually does not mean brilliance — it means underinvestment. There is almost certainly profitable acquisition available at a higher CAC that you are declining to buy, and a competitor willing to pay more will take those customers. The goal is a healthy ratio at the largest volume you can sustain, not the highest ratio you can post.

The LTV/CAC ratio tells you whether acquisition is profitable eventually. CAC payback period tells you when, and it is the one that determines whether you can afford to grow. Calculate it as CAC ÷ monthly gross profit per customer. A $200 CAC against a customer producing $40 of gross profit a month pays back in 5 months. The same $200 against $10 a month takes 20 months, and during those 20 months every new customer is a hole in your bank balance that has to be funded from somewhere. This is why two businesses with identical LTV/CAC ratios can have completely different fates. Fast payback lets acquisition spending recycle itself; slow payback means growth consumes cash faster the better it goes. If cash is tight, payback period is the more urgent of the two metrics.

Blended CAC divides all spend by all new customers, including the ones who arrived through word of mouth, organic search or direct traffic and cost nothing. It flatters the number and it hides the answer to the only question that matters for budgeting: what does the next customer cost? For that, look at paid CAC — spend divided by customers attributable to paid channels — and better still at marginal CAC, what an additional increment of budget buys. Both rise as you scale, because the cheapest, most intent-driven audiences get bought first. A CAC that stays flat while spend triples is usually a sign of measurement error rather than a miracle. Finally, watch for CAC that is falling for the wrong reason. Loosening the definition of a "customer" — counting free signups, or leads instead of closed deals — reduces CAC on paper while nothing improves. Whatever definition you pick, keep it stable, and make sure it is the same definition used in the LTV you compare it against. Comparing an LTV built from paying customers to a CAC built from signups produces a ratio that is pure fiction.