Stripe's current SaaS metrics guide defines a Magic Number as customer lifetime value divided by customer acquisition cost. The ratio can summarize whether estimated lifetime value covers acquisition cost, but it inherits every uncertainty in CAC, churn, margin, expansion, and the observation window. It should be presented as a model, not a promise.

VISUAL LESSON

What you will learn

  1. 01Calculate fully loaded CAC.
  2. 02Build a transparent LTV estimate.
  3. 03Interpret the ratio with sensitivity and companion metrics.
Lifetime value blocks balance against acquisition-cost blocks while margin and retention feed the value side
The Magic Number is only as credible as the customer, cost, margin, and lifetime assumptions beneath it.

ILLUSTRATIVE WORKED EXAMPLE

Work an illustrative LTV-to-CAC ratio

Acquisition spendIllustrative sales and marketing cost
$120k
New customersCAC = $3,000
40
Estimated LTVMargin-aware model
$6,000
Magic Number$6,000 ÷ $3,000
2.0×
Illustrative example—not a benchmark. Replace every sample value with your own campaign, market, and measurement data.

PRACTICAL INTERFACE MAP

Move from cohort costs to a sensitivity-tested ratio

CAC01Reconcile acquisition cost

Include agreed sales and marketing costs, define new customers, align the period, and separate blended from paid CAC.

LTV02Model lifetime contribution

Use ARPU or revenue, gross margin, churn or survival, expansion, refunds, and a stated horizon consistently.

Ratio03Divide and stress-test

Calculate LTV ÷ CAC, then vary retention, margin, cost, and cohort quality; show payback and cash alongside it.

Conceptual walkthrough. Labels, controls, and availability can vary by account, region, plan, and interface version; verify the current screen before acting.

STEP-BY-STEP LESSON

Cohort cost → margin-aware LTV → ratio → sensitivity and decision

ReconcileCustomers and acquisition cost
EstimateLifetime contribution
DecideRatio and downside case

THE LEAD ATLAS METHOD

Lead Atlas Data can research a focused list of business contacts for the customer's campaign, categories, locations, and market, while the growth team calculates acquisition economics from actual spend and customer records.See how custom list research works ↗
01

Define customer and cohort

Choose the acquisition cohort, customer unit, first-paid event, market, product, contract type, currency, and observation window. Resolve duplicates, upgrades, subsidiaries, free accounts, trials, reactivations, and refunds consistently.

Keep logo customers and subscriptions separate when one company can hold several subscriptions. Compare cohorts at the same age and preserve source channel without forcing unattributed customers into paid acquisition.

02

Calculate fully loaded CAC

Add the agreed acquisition costs for the cohort: media, agency, tools, content, events, sales compensation, commissions, onboarding sales support, and allocated overhead according to the finance policy. Divide by new paying customers attributed to the same scope.

Show paid, sales-assisted, organic, partner, and blended CAC separately when the business can support the mapping. Do not mix one quarter's spend with lifetime new customers or exclude failed acquisition work without disclosure.

03

Build a transparent LTV estimate

Choose a model based on customer revenue or ARPU, gross margin or contribution, churn or cohort survival, expansion, contraction, refunds, service costs, and a finite horizon where uncertainty is high. Reconcile it with observed cohorts.

Simple ARPU divided by churn can be a useful estimate under restrictive assumptions, but small churn changes create large lifetime changes. State whether LTV means revenue, gross profit, or contribution and never compare revenue LTV with margin-based CAC decisions without explanation.

04

Calculate and stress-test

Divide estimated LTV by CAC. In the illustrative example, $6,000 divided by $3,000 equals 2.0. Then calculate downside, working, and upside cases by varying margin, churn, expansion, acquisition cost, refunds, and time horizon.

A ratio above one in a revenue model does not automatically mean the business is profitable or liquid. Compare CAC payback, gross margin, retention, cash collection, sales cycle, fixed cost, concentration, and cohort size.

05

Turn the model into a decision

Diagnose whether acquisition cost, activation, price, expansion, churn, margin, or service cost drives the range. Assign one action and forecast the specific input it should change, then compare the next mature cohort with the preregistered expectation.

Deliverable: cohort dictionary, customer reconciliation, CAC ledger and allocation policy, LTV model, margin and retention assumptions, Magic Number, sensitivity table, payback and cash view, caveats, one prioritized action, and model owner.

THE TAKEAWAY

Build CAC and margin-aware LTV from consistent cohorts, show the assumptions and sensitivity range, and use the ratio with payback, retention, margin, and cash—not alone.

OFFICIAL REFERENCES

Check the platform’s current instructions.

Platform labels, eligibility, and workflows can change. These official help pages were used to validate this lesson.