AnalyticsCAC, LTV, ROAS and marginIntermediateAnalyses your data

CAC and payback calculation with validation

Calculates CAC and payback from your inputs, shows every formula, and checks that definitions are consistent before the number is quoted.

For: Performance marketers, Marketing analysts, Growth marketers · Works with: Any capable chat model (ChatGPT, Claude, Gemini, others), Google Sheets / Excel

Public beta. This prompt was drafted with AI assistance and checked by automated rules, but it has not been reviewed or tested by a person yet. Treat it as a starting point and check the output. It is hidden from search engines while in beta. Use the “Was this prompt useful?” box to tell us what works.

Your prompt

Act as a finance-minded marketing analyst. Calculate customer acquisition cost (CAC) and payback period using ONLY the inputs below. Inputs (period: Q3 2026): - Marketing spend included: paid media, creative production and marketing tools, total 120000 USD - New customers acquired: 800, defined as first paid order in the period, excluding reactivations - Average gross margin per customer per month (or first-order margin): $18 per customer per month - Other inputs I can provide: none Tasks: 1. Restate the definitions you will use and flag anything ambiguous (for example whether sales salaries, tools and agency fees are included, and whether "new customers" excludes reactivations). 2. Compute blended CAC, showing the formula and the arithmetic step by step. 3. Compute payback in months using margin (not revenue) if margin was provided; if not, say it cannot be computed and what to supply. Show the formula. 4. Recalculate everything a second time and confirm the results match; report any rounding choices. 5. Show how CAC changes under two alternative spend definitions (with and without marketing salaries) so I see how sensitive it is. 6. List what the figure does NOT tell me (for example channel-level CAC, quality of customers, cohort behaviour) and the data required. Rules: do not invent inputs, benchmarks or "healthy" thresholds. If inputs are missing or not provided, stop and list what is needed. State assumptions. Verify all arithmetic. CAC is an accounting ratio, not evidence that the spend caused the customers.

Customize

The fields start with example values so you can see how the prompt works. Everything stays in your browser.

Reporting period.

What spend counts.

Total spend for the period.

Currency.

Count for the period.

Definition.

Margin, not revenue.

Anything else.

A cost whose inclusion changes CAC.

Example of what to expect

Illustrative only. It describes the kind of result this prompt aims for; real output varies by tool, model and run.

Definitions, blended CAC with step-by-step arithmetic (here 120000 / 800 = 150, illustrative), payback computed from margin, a second-pass check, sensitivity to cost definitions and a 'what this does not tell you' list.

Expected format: Definitions, CAC and payback calculations, check, sensitivity, caveats.

How to use it

  1. Agree your CAC definition with finance first.
  2. Verify the arithmetic in a spreadsheet.
  3. Compare with the CAC calculator.

Limitations

  • Blended CAC hides channel and cohort differences.
  • Payback based on average margin can mislead if customers differ widely.

Platform notes

Any capable chat model (ChatGPT, Claude, Gemini, others)

Official docs read · checked 2026-10-11

Works in any capable chat model. Paste a small anonymised sample and recompute the key numbers yourself: chat models can misread columns or miscalculate.

General notes on Any capable chat model (ChatGPT, Claude, Gemini, others)
  • These prompts are plain text and work in any chat assistant. For analytics prompts, paste a small, anonymised export; a chat model can misread columns or miscalculate, so recompute key numbers yourself.

Google Sheets / Excel

Not verified: third-party guidance only · checked 2026-10-11

Formula syntax is shared across Google Sheets and Excel for the functions used here, but argument separators and function availability depend on your locale and version; test on a small range first.

General notes on Google Sheets / Excel
  • Formulas are written for common functions in both products. Locale settings (decimal and argument separators) can change what you must type.

Source, license and attribution

Origin
Original by MarketerTools
Publisher
MarketerTools
License
Original work by MarketerTools, free to copy and use. Informed by the linked documentation; no third-party text is reproduced.
Platform assumptions checked
2026-10-11

Documentation and references behind this prompt

These informed the structure and the platform notes. A reference is not a license, and no third-party prompt text is copied here.

Spotted an attribution error, or are you a source owner with a request? Use the chat button at the bottom right and quote prompt ID ana-026. We will correct or remove it.

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