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CAC Payback Calculator — Months to Recoup

Calculate how many months to recover customer acquisition cost. CAC payback under 12 months signals healthy SaaS unit economics and growth strategy.

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CAC Payback Period

Monthly gross profit / cust

$75

Payback period

6.7 months

Healthy SaaS: CAC payback under 12 months. Above 18 months you're burning cash for too long before each customer turns profitable — slow your growth or fix the unit economics.

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About this tool

Payback measures cash burn, not profitability

A profitable SaaS product can still destroy cash. Profitability counts revenue after all costs; payback measures how long capital sits tied up in acquisition before that customer begins generating enough gross profit to recover what you spent getting them. If payback is 24 months but your runway is 18, you run out before the customer pays for themselves.

A real example: $500 CAC, 75% margins

You spend $500 to acquire a customer. Your ARPU is $100/month, and gross margin is 75%, so each customer generates $75/month in gross profit toward future acquisition. Payback period = $500 ÷ $75 = 6.7 months. They're cash-positive by month 7.

Now raise CAC to $2000 (bigger sales team). Same customer: $2000 ÷ $75 = 26.7 months. That customer doesn't turn cash-positive for two years. Your balance sheet can't afford to wait that long, even if they eventually stay for five years and generate $4500 in gross profit.

This calculator divides CAC by monthly gross profit per customer

Input your CAC, ARPU, and gross margin percentage. The formula: CAC ÷ (ARPU × gross margin) = months. Healthy SaaS targets payback under 12 months. Above 18 months, you're betting that retention, LTV, and future pricing increases can offset the capital intensity of your acquisition model — a bet that breaks most companies.

The result assumes gross margin is consistent from month one. It does not account for discount rates (time value of money), expansion revenue, logo churn, or the cash cost of payroll cliffs.

What this tool does not model

Payback assumes the customer reaches stabilized ARPU immediately and churns at zero through the payback window — neither true in practice. It ignores the operating leverage of shared overhead (support, infrastructure). If you're in early-stage with high CAC and low ARPU, payback will look terrifying; that doesn't mean the business is doomed, only that you need either better retention or higher pricing to close the gap. Compare your payback to your LTV and your actual monthly cash burn to make an acquisition trade-off decision.

See also: LTV Calculator, ROAS Calculator.

How to use the CAC Payback Period Calculator

Takes about a minute. No signup, no download, your data stays in your browser.

  1. 1
    Open the tool. Scroll up to the CAC Payback Period Calculator above — it loads instantly in your browser, no install needed.
  2. 2
    Enter your values. The fields come pre-filled with realistic defaults so you can see how it works — replace them with your own numbers.
  3. 3
    Read the result. The output updates instantly. Copy or share it — nothing is uploaded to a server, everything stays on your device.

Frequently asked questions

Common questions about the CAC Payback Period Calculator.

What's the difference between CAC payback and ROI?

CAC payback measures months until the customer generates enough gross profit to recover acquisition cost. ROI is a ratio of profit to cost. A customer with $500 CAC and $75/month gross profit breaks even in payback after 6.7 months, but if they stay for 5 years they generate $4500 gross profit, an 800% ROI. Both matter: payback tells you if your cash can survive the wait; ROI tells you if the wait is worth it.

Do I use revenue or gross margin in the formula?

Always gross margin. The formula is CAC ÷ (ARPU × gross margin %). If your ARPU is $100 but you pay 50% in COGS and delivery costs, your gross margin is 50%, so monthly gross profit is $50. That $50 is what funds future acquisition, not the full $100 revenue. Using revenue overstates how fast you recover CAC.

What if my ARPU or gross margin is zero?

If monthly gross profit (ARPU × margin %) is zero or negative, payback is infinite — you can never recover acquisition cost from that customer because they generate no positive cash. This is a red flag for product-market fit, not a calculator error. Fix the unit economics first; payback math will follow.

Why is 12 months the benchmark?

Most SaaS companies can finance 12 months of customer acquisition on their operating margin or venture capital. Above 18 months, payback becomes risky for bootstrapped or public companies; your balance sheet can't withstand the capital intensity. Longer payback is possible if you have series C+ funding, expansion revenue, or net negative churn — but you're always competing against benchmarks and lender expectations.

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