Payback Calculator
Cohort model for subscription & one-time-purchase apps — net of store commission, refunds and trial conversion. Built for UA bid decisions.
Inputs · Plan A
Results
Net LTV / acquired user
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ROI (LTV ÷ CPA)
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Payback
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First-period recovery
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Cumulative net revenue
CPA cost line
Period breakdown
| # | Charge day | Survival | Commission | Net revenue | Cumulative |
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Model assumptions (edit compute() in core.js if yours differ):
① CPA is the cost per acquired user: per paying user without a trial, per trial user with one;
② net revenue = price × (1 − refund rate) × (1 − store commission); the paying base decays as trial conversion × geometric renewal;
③ Standard commission drops 30% → 15% once a subscription survives one full year (52 weekly / 12 monthly / 1 yearly period);
④ charge day = trial length + period × cycle days (7 / 30 / 365); payback is counted on charge days;
⑤ one-time purchases have no renewals — first-period revenue only.