Growth tool

CAC Payback Calculator

Calculate CAC payback using spend, qualified leads, close rate, gross margin, and churn.

$ run payback

Check CAC payback before increasing spend.

A channel can look efficient on CPL and still create a weak payback period. I use this to check whether the same plan still pays back after close rate, gross margin, and churn are included.

Estimated CAC payback

1.9 monthsStrong enough to test scale if lead quality and sales capacity hold.
Estimated CPL
750
New customers
16
Estimated CAC
21,875
Monthly gross profit/customer
11,250
Year-one gross profit/customer
114,809
Year-one profit after CAC
92,934
Estimated LTV:CAC
17.1x
Monthly gross profit from new customers
1,80,000
Payback band
Scale test

Scenario comparison

ScenarioClose rateChurnCACPaybackLTV:CAC
Current input4.0%3.0%21,8751.9 mo17.1x
Conservative3.0%4.0%29,1672.6 mo9.6x
Better conversion5.0%2.0%17,5001.6 mo32.1x

Conservative lowers the close rate by 25% and adds one churn point. Better conversion raises close rate by 25% and removes one churn point. If the answer changes sharply, the channel needs diagnosis before budget debate.

How I read the payback band

< 6 monthsUsually room to test more volume if lead quality and sales capacity are real.
6-12 monthsCan work for sticky B2B, but retention and sales cycle need a closer look.
12-18 monthsNeeds stronger proof before adding spend. Check conversion, discounting, and onboarding.
18+ monthsUsually a pricing, margin, retention, quality, or handoff problem.

Use the same currency across spend and revenue. The calculator does not store or send your inputs anywhere.

What CAC payback means

CAC payback is the number of months it takes to earn back the cost of acquiring a customer, using gross profit rather than revenue. If the payback is long, the channel may still work, but the business has to carry the cash gap.

Why I built it this way

I have seen too many channel reviews stop at CPL, lead volume, or platform CPA. Those numbers are not useless, but they are too early in the route. A paid channel has to survive the path from click to lead, lead to customer, revenue to gross profit, and first month to retained account.

Inputs used in the calculator

  • Monthly media spend: the amount paid to platforms such as Google, Meta, LinkedIn, or another acquisition channel.
  • Monthly non-media cost: agency fees, contractor cost, tools, list cost, landing page work, or other acquisition cost you want included in CAC.
  • Qualified leads: leads that meet the bar your sales team would actually work, not every form fill.
  • Lead-to-customer rate: the percentage of qualified leads that become paying customers.
  • Monthly revenue per customer: average monthly revenue from a new customer or account.
  • Gross margin: the portion of revenue left after delivery cost.
  • Monthly churn: the share of customers expected to leave each month.
  • Target payback: the maximum payback period you are comfortable with before the channel needs a second look.

How to read the result

The headline number is only the first read. If payback is strong but LTV:CAC is weak, churn is eating the upside. If LTV:CAC is strong but monthly gross profit from new customers is small, the channel may be fine but too small to matter. If the conservative scenario breaks the case, I would check whether the close rate in the plan is coming from a narrow set of unusually good leads.

A quick example

Say a channel spends 300,000 a month, carries another 50,000 in operating cost, produces 400 qualified leads, and closes 4% of them. That is 16 customers. If each customer brings 15,000 in monthly revenue at 75% gross margin, CAC payback is about 1.9 months. If the close rate slips to 3% and churn rises to 4%, CAC moves to about 29,167 and the LTV:CAC ratio drops sharply. The channel may still work, but it now depends on sales reliably turning that lead source into retained accounts.

Formula

Estimated CPL = media spend / qualified leads. Estimated CAC = (media spend plus non-media acquisition cost) / expected new customers. Payback months = CAC / monthly gross profit per customer. Year-one gross profit applies the monthly churn assumption across twelve months. Estimated LTV = monthly gross profit per customer / monthly churn. LTV:CAC = estimated LTV / CAC. Monthly gross profit from new customers = new customers times monthly gross profit per customer.

What I would check next

  • If CPL is low and payback is weak, check whether the qualification bar is too loose.
  • If CAC is acceptable but year-one profit is thin, check margin, retention, onboarding, and discounting.
  • If the model depends on a high close rate, check whether sales is seeing the same buying intent marketing is reporting.
  • If the conservative scenario changes the answer too much, inspect the lead mix rather than debating a single blended CPL.
  • If payback looks excellent, check volume limits before assuming the channel can scale linearly.

Methodology and limitations

This is a rough calculator, not a forecast. It ignores sales cycle lag, expansion revenue, refunds, delayed churn, cohort differences, attribution gaps, and sales follow-up quality. It is still useful because it forces the channel conversation to include conversion rate, margin, and retention instead of stopping at lead cost.