How to measure CAC Payback Period

The number of months of gross profit from a customer required to recover the cost of acquiring them.

Payback = CAC ÷ (ARPU × Gross Margin)

Why it matters: Skok's rule of thumb: under 12 months is healthy for SMB SaaS. Long payback ties up cash and forces you to raise more to fund growth — it's the cash-flow lens on unit economics.

2 tools that produce Payback

Side-by-side: how each tool produces this number, what to read before adopting, and where to find the official docs. Saasly does not integrate with these tools — this is a reference so you can pick the right one for your stack.

ToolCategoryHow it produces PaybackPricing
StripeBilling platformComputed (SQL / export)Pay-as-you-go (2.
Saasly CalculatorManual calculatorManual entryFree forever, no signup.

Per-tool: what to know before you plug it in

Stripe

Computed (SQL / export)

Billing platform

Subscription billing platform with built-in dashboards and SQL analytics (Sigma).

Before you adopt: Stripe supplies ARPU; you supply CAC and gross margin from outside the billing data. Compute in Sigma (SQL) or export. Use a gross-margin-adjusted payback, not raw revenue — ignoring COGS understates the true months-to-recover.
Pricing: Pay-as-you-go (2.9% + $0.30 per charge). Sigma analytics: free up to 1K charges/mo, then $0.02/charge.
Official docs for Payback Stripe home

Saasly Calculator

Manual entry

Manual calculator

Manual-entry calculator that computes the core SaaS metrics with Skok-tier classification.

Before you adopt: Enter CAC, ARPU, and gross margin — get the gross-margin-adjusted payback period in months. Pairs with the LTV:CAC view to see whether a long payback is justified by a high lifetime value.
Pricing: Free forever, no signup.
Official docs for Payback Saasly Calculator home

Already have your numbers? Run the math.

The Saasly Calculator computes Payback (and 15 other SaaS metrics) from manual input — useful when you've pulled the underlying numbers out of one of the tools above and want a quick sanity check with industry benchmark percentiles.

Open the calculator

Other metrics

How to measure Customer Lifetime Value
The total gross profit a single customer is expected to generate over their entire relationship with you.
How to measure Customer Acquisition Cost
The fully-loaded cost of acquiring one paying customer in a given period.
How to measure Monthly Recurring Revenue
The normalized monthly value of every active subscription, regardless of billing period.
How to measure Customer Churn Rate
The percentage of customers who cancel in a given period. Counts logos, not dollars.
How to measure Net Revenue Retention
How much revenue a cohort of existing customers generates compared to where they started — including expansion, contraction, and churn.
How to measure SaaS Quick Ratio
The ratio of revenue gained (new + expansion) to revenue lost (churn + contraction) in a period.
How to measure Magic Number
Annualized net-new ARR generated for each dollar of the prior quarter's sales & marketing spend.
How to measure Gross Margin
The percentage of revenue left after the direct cost of delivering the service (hosting, support, payment fees, third-party APIs).
How to measure Trial-to-Paid Conversion
The percentage of users who start a trial and become paying customers.
How to measure Net Promoter Score
A survey-based score from the 0–10 'how likely are you to recommend us?' question, taking promoters (9–10) minus detractors (0–6).
How to measure DAU/MAU Ratio
The share of monthly active users who use the product on a given day — the standard 'stickiness' measure.