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Marketing Payback Calculator

Enter the CAC and monthly margin to get the payback period.

Result

7.50 mo

How it is calculated

The payback period is months = CAC ÷ monthly margin per customer. CAC is what it cost on average to win one customer: total sales and marketing spend divided by the number of new customers it brought in. Monthly margin is the money left from one customer each month after the direct costs of serving them, such as hosting, support or cost of goods. Both are in the same currency and the answer is in months, shown with two decimals. CAC cannot be negative, and the monthly margin must be above zero, otherwise no result is shown. The formula assumes the customer stays long enough and that the margin is constant; it ignores churn, discounting and upsells.

Worked example

Suppose acquiring a customer costs 450 and each customer leaves 60 of margin per month. Payback = 450 ÷ 60 = 7.50 mo. After 7 months the business has recovered 420, and during the 8th month the remaining 30 comes back, so the customer is paid off halfway through month 8. Every month after that is profit, provided the customer has not cancelled before reaching that point.

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Common mistakes

  • Using revenue per month instead of gross margin. Subtracting delivery costs first matters, and revenue alone makes the payback look shorter than it is.
  • Entering annual margin in the monthly field, which makes the payback twelve times too short.
  • Calculating CAC from ad spend only. Salaries, tools and agency fees for acquisition belong in the cost, otherwise the payback looks better than reality.
  • Ignoring churn. If many customers leave before month 7.5, the average customer never pays back, even though the formula says it does.
  • Blending customers from different channels or plans into one average. A cheap channel and an expensive one can hide each other, so run each separately.

Sources

About this calculator

The marketing payback period answers a simple question: how many months does it take for a newly acquired customer to earn back what it cost to acquire them? The formula is CAC (customer acquisition cost) ÷ monthly gross margin per customer — so a $300 CAC against $50 of monthly margin per customer gives a 6-month payback.

Subscription and SaaS businesses, growth marketers, and investors evaluating unit economics watch this number closely because it directly measures cash-flow risk: a payback period under roughly 12 months is generally considered healthy for SaaS, while longer paybacks mean the company is fronting more cash per customer before that spend turns profitable, which matters a lot for how fast it can safely scale acquisition spend.

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Comments (1)

  • Editorial team

    Put the payback next to how long customers actually stay. A rough rule is average lifetime in months equals one divided by monthly churn, so 5 percent churn means about 20 months, and a 7.5-month payback leaves a comfortable margin, while 15 percent churn gives under 7 months and the same payback never really closes. Do you track churn by channel, or only for the whole customer base?

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