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CAC Payback Period Calculator

How many months until a customer pays back what it cost to acquire them? Enter CAC, monthly ARPA and gross margin to get your payback period and how it compares to the 12-month bar.

Your numbers

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CAC payback period
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Gross profit / mo
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Verdict
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On revenue (no margin)
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vs 12-month bar
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The CAC payback formula

CAC payback (months) = CAC ÷ (monthly ARPA × gross margin). The key detail is gross margin: you recover CAC out of gross profit, not revenue, because serving the customer has a cost. A $1,200 CAC against $120 ARPA at 80% margin is $96 of monthly gross profit, a 12.5-month payback, not the 10 months revenue alone would suggest.

A common investor rule of thumb is payback under ~12 months. Actual results are slower: the median B2B SaaS company took 16 months to pay back CAC in 2025, and the top quartile 10 months (Benchmarkit 2026). SMB should aim lower (faster payback, since SMB churns more); higher-ACV and enterprise can tolerate 12 to 18+ months because those customers stay longer. The reason it matters: long payback strains cash, you fund acquisition today and wait months to get it back, so fast growth with slow payback burns money quickly.

Worked example: $1,200 CAC on a $120 plan

A SaaS company spends $1,200 to win a customer who pays $120 a month at an 80% gross margin.

Default inputs of the calculator above. Change any input to run your own numbers.
CAC$1,200
Monthly ARPA$120
Gross margin80%
Gross profit per month$120 × 80% = $96/mo
Payback on revenue (no margin)$1,200 ÷ $120 = 10.0 mo
vs 12-month bar+0.5 mo (verdict: Watch)
CAC payback period$1,200 ÷ $96 = 12.5 months

Payback is one half of unit economics; pair it with the LTV:CAC ratio (is the customer profitable over their whole life?). See CAC payback period explained for benchmarks and how to improve it.

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Frequently asked questions

How do you calculate CAC payback?
CAC payback (months) = CAC ÷ (monthly ARPA × gross margin). A $1,200 CAC, $120 ARPA and 80% gross margin give $1,200 ÷ $96 = 12.5 months.
Should CAC payback use revenue or gross margin?
Gross margin. You recover acquisition cost out of gross profit, because serving the customer costs money. On revenue alone the same example reads 10.0 months, which flatters it by 2.5 months.
What is a good CAC payback period?
A common rule of thumb is under about 12 months. The 2025 median for B2B SaaS was 16 months and the top quartile 10 months (Benchmarkit 2026). SMB should aim lower because SMB customers churn more; higher-ACV and enterprise SaaS can carry 12 to 18 months or more. CAC payback period explained has the benchmarks by segment.
How do you calculate CAC for the payback formula?
Divide total sales and marketing spend in a period, salaries and tools included, by the new customers won in that period. Use the fully loaded figure, not ad spend alone. See what CAC is.
What is the difference between CAC payback and LTV:CAC?
Payback measures how fast you get the acquisition cost back; LTV:CAC measures how much a customer is worth over their whole life relative to that cost. Check both with the LTV:CAC calculator.
How do I calculate CAC payback in Excel?
With CAC in B1, monthly ARPA in B2 and gross margin as a percentage in B3, use =B1/(B2*B3) for the payback in months.
Cite this page

Citation

Adlega. "CAC Payback Period Calculator and Formula (SaaS)." Updated October 22, 2026. https://adlega.com/blog/tools/cac-payback/

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<a href="https://adlega.com/blog/tools/cac-payback/">CAC Payback Period Calculator and Formula (SaaS)</a> (Adlega, updated October 22, 2026)

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