CAC calculator with the ratio and the payback finance asks for

Customer acquisition cost is everything you spent to win new customers in a period, divided by the number of customers you won. The division is trivial; the definitions are where teams disagree. Marketing usually reports paid CAC, media spend divided by customers, because that is the number the campaigns control. Finance wants fully loaded CAC: media, agency fees, salaries of the people doing marketing and sales, the software they use, sometimes the free trial's hosting cost. Both are right; label which one you mean.

Two timing rules keep the number honest. Count customers who were won in the period, not who signed up as leads. And match the spend to the same period, or shift it by your sales cycle: with a 60-day cycle, this month's customers came from spend two months ago.

An €800 CAC is excellent for a customer worth €20,000 over their lifetime and fatal for one worth €500. The number that decides is the ratio of lifetime value to CAC, and the rule of thumb is 3:1. Below about 1.5:1 the business loses money on growth; above 5:1 it is usually spending too little on it.

The second number is payback: how many months of gross margin from one customer it takes to earn back the cost of acquiring them. CAC divided by monthly gross profit per customer. Under twelve months is comfortable for most SaaS and service businesses; over eighteen means growth has to be financed and every churned customer is a loss. The calculator returns both once you enter revenue per customer, lifetime and gross margin.

CAC is a chain: cost per click, conversion rate to lead, lead-to-customer rate. Each link is a lever, and the biggest one is usually not the media price.

• Close rate. Raising lead-to-customer from 20 to 25 percent cuts CAC by a fifth on the same spend. Qualification and follow-up speed move it more than campaigns do.
• Channel mix. Blended CAC hides a channel producing customers at €400 next to one at €2,000. Knowing which is which requires the ad click to be attached to the customer record; most CRMs do not have it.
• Tracking. If the platform sees 60 percent of your leads, it optimises towards the wrong 60 percent. The CAC the CRM reports stays right; the bidding that produces it gets worse.