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CAC payback period

Also called: CAC payback, payback period, months to recover CAC

How many months of gross profit from a new customer it takes to earn back what it cost to acquire them: CAC ÷ (monthly revenue per customer × gross margin).

The CAC payback period is the number of months a new customer needs to pay back what it cost to win them. The formula: payback (months) = CAC ÷ (average monthly revenue per customer × gross margin). If winning a customer costs 2,000 and they leave you 500 of gross profit a month, payback is 4 months.

For a bootstrapped business payback matters even more than the LTV:CAC ratio, because it's about cash. Until a customer has paid back their CAC, the money spent on them is a loan the business has made to itself. A short payback lets a company fund its own growth: the money comes back in a few months and can be spent again on the next customers. A long payback means every extra customer ties up cash for a long time, which only works with savings or investors behind you.

Rough guides: a few months is excellent for a small business, under 12 months is usually considered good for SaaS, and anything longer than the typical customer lifetime means customers never pay back at all. Annual plans shorten payback dramatically, because the customer pays a year's gross profit on day one.

Example

A new GarageDesk shop in year 2 pays 750 UAH a month and costs about 117 UAH a month to serve, leaving about 633 UAH of gross profit.

  • Referral (1,800 UAH per shop the program really added): payback = 1,800 / 633 ≈ 2.8 months.
  • Ads (about 5,000 UAH per shop): payback = 5,000 / 633 ≈ 7.9 months.
  • Yearly plan: a shop that pays 7,500 UAH up front covers either CAC on the first day.

With an average lifetime of about 25 months both channels pay back, but referral money comes back almost three times faster and can be spent again on the next shops.

Common mistakes

  • Dividing by revenue instead of gross profit. Payback on revenue looks shorter than it really is.
  • Forgetting discounts and free months. Use what the customer actually pays in the first months.
  • Ignoring churn during payback. Some customers leave before they pay back; a long payback makes this worse.
  • Looking only at the average. A channel with an 18-month payback can hide behind a cheap one.