What does the CAC Payback Period Calculator calculate?

Stub entry — see hand-written methodology. Computes how many months to recover CAC from gross profit, and the LTV:CAC ratio.

What inputs does the CAC Payback Period Calculator need?

It takes 4 inputs: cac, arpu, grossMargin (default 80), monthlyChurn (default 5). Outputs returned: paybackMonths, ltv, ltvCacRatio.

Can I verify the CAC Payback Period Calculator with a worked example?

Yes. With cac = $200, arpu = $50, grossMargin = 80%, monthlyChurn = 4%. the tool returns payback = 5 months, ltv = $1,000, ltv:cac = 5×.

Where does the CAC Payback Period Calculator get its benchmark data?

Reference data is sourced from: OpenView SaaS Benchmarks 2024 (as of 2024).

What can the CAC Payback Period Calculator not tell me?

Known limitations: Payback-month percentile benchmarks vary sharply by stage and ACV. Compare within peer group.

Methodology: CAC Payback Calculator

1. Scope

The CAC Payback Calculator reports how many months of gross profit per customer are needed to recover the cost of acquiring that customer. It is the margin-adjusted version of the payback formula — the one relevant to capital-efficiency decisions. It operates at the aggregate level; cohort-level payback is more accurate but requires per-customer timestamps the tool does not ingest.

2. Inputs and outputs

Inputs: CAC (blended acquisition cost per paying customer), ARPU, gross margin, monthly churn rate. Outputs: payback in months, LTV (gross-profit form), LTV:CAC ratio, and a health band benchmarked against published SaaS percentiles.

Engine source: src/lib/cac-payback-calculator/engine.ts.

3. Formula / scoring logic

payback_months  = CAC / (ARPU * gross_margin)
LTV             = (ARPU * gross_margin) / monthly_churn
LTV_CAC_ratio   = LTV / CAC

The gross-margin multiplier in the denominator is load-bearing. Without it, payback is "months until CAC is recovered in gross revenue," which ignores cost-to-serve and systematically understates the recovery horizon. Include it unless the business is software-margin-trivial (e.g. infrastructure-light information products where gross margin is ≈ 100%).

4. Assumptions

Aggregate, not cohort. Blended CAC hides the fact that organic and paid customers have vastly different payback profiles. Segment explicitly if the mix is meaningful.
Memoryless churn. LTV formula uses the same constant-churn assumption as elsewhere on this site.
Gross margin is customer-variable-cost margin. Payment-processing, inference, hosting, fulfilment. Excludes overhead.
ARPU is the price the customer actually pays. Annual plans should be normalised to monthly equivalent.
CAC is fully-loaded. Sales salaries, ad spend, tooling, attributable content investment.

5. Data sources

OpenView SaaS Benchmarks 2024 — CAC payback percentiles by stage and GTM motion (12-month median for mature B2B SaaS; higher for early-stage or long-sales-cycle enterprise).
SaaS Capital Annual Survey — bootstrapped and capital-efficient payback percentiles.
Paddle SaaS Benchmarks 2024 — B2B vs B2C norms.

6. Known limitations

Aggregate blending is misleading when the mix is asymmetric. If 70% of acquisition is organic (near-zero CAC) and 30% is paid (high CAC), the aggregate payback number reflects neither channel's economics.
Cohort-level payback requires data the tool does not ingest. Cohort payback is the fraction of CAC recovered from gross profit generated by the specific cohort up to month m. Computing it needs per-customer signup and gross-profit timestamps.
12-month payback is a rule of thumb, not a law. Benchmarks vary by stage: top-quartile bootstrapped SaaS often clears payback in 3–6 months; enterprise SaaS routinely runs 18–24 months.
Margin timing is ignored. Annual plans have payback denominated in months of revenue but collected upfront. A more accurate cash-payback would discount future months by a cost-of-capital rate — this tool reports nominal payback.

7. Reproducibility

Input
CAC = $200, ARPU = $50/mo, gross_margin = 80%, monthly_churn = 4%.

Expected output
payback = 5 months (= $200 / ($50 × 0.80)). LTV = $1,000. LTV:CAC = 5× — healthy for a bootstrapped SaaS and comfortably above the OpenView 2024 median for the stage.

8. Change log

2026-04-24methodology page first published. Gross-margin-adjusted payback and LTV:CAC documented, with cohort-vs-aggregate caveat.

Worked example

Run live against the same engine this site ships (/engines/cac-payback-calculator.js). The inputs and outputs below are recomputed on every build and independently re-verified in CI — they are never hand-authored.

Input

tool: cac_payback_calculator
cac: 2400
arpu_monthly: 129
gross_margin_percent: 75
target_payback_months: 12

Output

monthlyGrossProfit: 96.75
paybackMonths: 24.8
estimatedLtv24m: 2322
ltvCacRatio24m: 0.97
paybackHealth: Danger
ltvCacHealth: Danger
monthsToBreakEven: 24.8
vsTargetDeltaMonths: 12.8
guidance: Payback at 24.8 months is unsustainable. Pause heavy acquisition spend and fix CAC or improve ARPU/margins first.

Frequently asked questions

What does the CAC Payback Period Calculator calculate?: Stub entry — see hand-written methodology. Computes how many months to recover CAC from gross profit, and the LTV:CAC ratio.
What inputs does the CAC Payback Period Calculator need?: It takes 4 inputs: cac, arpu, grossMargin (default 80), monthlyChurn (default 5). Outputs returned: paybackMonths, ltv, ltvCacRatio.
What formula does the CAC Payback Period Calculator use?: The exact computation is: payback_months = cac / (arpu * gross_margin); ltv = (arpu * gross_margin) / monthly_churn; ltv_cac_ratio = ltv / cac
Can I verify the CAC Payback Period Calculator with a worked example?: Yes. With cac = $200, arpu = $50, grossMargin = 80%, monthlyChurn = 4%. the tool returns payback = 5 months, ltv = $1,000, ltv:cac = 5×.
Where does the CAC Payback Period Calculator get its benchmark data?: Reference data is sourced from: OpenView SaaS Benchmarks 2024 (as of 2024).
What can the CAC Payback Period Calculator not tell me?: Known limitations: Payback-month percentile benchmarks vary sharply by stage and ACV. Compare within peer group.