CAC, cohorts, LTV, and payback

Canonical formulas

New-customer CAC = attributable acquisition spend / acquired customers. Repeat-purchase rate = customers with a repeat order / eligible first-order customers. Cohort LTV = discounted cohort contribution / customers in the cohort. LTV/CAC = cohort LTV / CAC. Payback is the first period where cumulative customer contribution is at least CAC. Maximum allowable CAC is discounted future contribution before acquisition cost.

Data requirements and privacy

Calculations require an approved first-party identity domain, seller-owned opaque references, eligible order history, attributable campaign spend, contribution inputs, observation dates, and a declared discount policy. Marketplace buyer identity must not be repurposed for direct marketing or cross-channel matching.

Unavailable state and example

A missing or zero acquired-customer denominator makes CAC and dependent ratios unavailable. Immature cohorts show only supported horizons; suppressed small groups must not be reverse engineered.

Example: 60,000 RUB of attributable spend and 120 acquired customers gives CAC of 500 RUB. If cumulative contribution per customer reaches 530 RUB in month four, modeled payback is month four. This does not prove future retention and must show the cohort dates and maturity.