Payback calculators
CAC Payback Calculator
Built the growth engine that took cnvrg.io to its acquisition by Intel.
How many months of gross profit does a new customer need to repay what you spent to win them? Enter one period of your own numbers; the formulas are on the page.
CAC payback calculator
How many months of gross profit a new customer needs to repay what you spent to acquire them.
Your own numbers from one period. No benchmark is implied.
How this is calculated
CAC = sales and marketing spend ÷ new customersMonthly gross profit per customer = ARPA × gross marginCAC payback (months) = CAC ÷ monthly gross profit per customer
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Enter your own numbers or load an example. The result will show its assumptions and limitations.
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What CAC payback answers
CAC payback is the number of months a new customer’s gross profit takes to repay the sales and marketing spend that acquired them. It tells a founder or CFO how long cash is tied up in growth before it comes back.
How the calculator works
CAC is all sales and marketing spend in a period divided by the new customers won in the same period. Monthly gross profit per customer is new monthly revenue per customer (ARPA) times gross margin. Payback is CAC divided by that monthly gross profit. The calculator also shows the revenue-basis payback, which ignores gross margin, because many decks quote that number.
A worked example with hypothetical numbers
Spend of 60,000 in a quarter that wins 20 new customers gives a CAC of 3,000. At 500 a month per customer and an 80% gross margin, each customer returns 400 a month in gross profit, so payback is 3,000 ÷ 400 = 7.5 months. These numbers illustrate the arithmetic; they are not a benchmark or a client result.
What the result does not tell you
Payback assumes the customer stays. A customer who churns before the payback month never repays its CAC, so check early churn with the LTV:CAC calculator. A blended CAC can also hide one expensive channel: split spend and customers by channel before cutting anything.
Turn the result into a next step
If payback is longer than your cash allows, the cause usually sits in one of three places: the cost of acquisition, conversion through the funnel, or the value a customer keeps paying. The CAC payback diagnostic guide shows how to tell which one moved.
CAC payback questions
What counts as sales and marketing spend?
Everything you spent to win new customers in the period: media, sales and marketing salaries, tools, agencies and contractors. Use the same period for the spend and for the new customers.
Should I use gross margin or revenue?
Gross margin. Revenue-basis payback looks shorter because it ignores the cost of serving the customer. The calculator shows both so you can see the gap.
Is there a good CAC payback benchmark?
This calculator does not supply one. Published benchmarks vary by segment, contract size and year, so compare your result with your own cash position and what your board expects.
Does the calculator store or send my numbers?
No. It runs in your browser. Nothing is sent unless you choose to send the result to me, and a share link keeps your numbers after the # sign, which browsers do not send to this site.
Can an AI agent run this calculator?
Yes. The same calculation is available as the run_calculator tool on this site's MCP server and at GET /api/v1/calculators?id=cac, with the same inputs, formulas and limits as this page.
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I personally review the numbers behind the result, agree the scope with you and deliver the work. Bring the questions the calculator raised.