Tools
CPI & ROAS Calculator
Calculate acquisition efficiency and revenue recovery from one paid-install cohort. Keep spend, installs and cumulative revenue aligned to the same attribution window.
Cohort Economics
Connect Cost To Return.
CPI, cumulative ROAS and a transparent payback scenario for your cohort.
The CPI And ROAS Formula
CPI = spend ÷ installs. ROAS at day N = cumulative cohort revenue through day N ÷ spend × 100%. IPM = installs ÷ impressions × 1,000; therefore eCPM = CPI × IPM. An entered CPM without IPM is an assumption, not independently observed eCPM.
Payback is the first modeled day at which cumulative revenue equals spend. We interpolate between supplied revenue anchors and, when necessary, extend the D7–D30 slope: day 30 + (spend − D30 revenue) ÷ ((D30 revenue − D7 revenue) ÷ 23). With no later revenue growth, payback is not estimable.
Do not mix campaign-day revenue with install-cohort revenue. SKAN modeled installs and deterministically attributed installs may use different windows: reconcile the denominator before drawing conclusions. A linear revenue extension can overstate late-life recovery and does not include margin, financing or changing monetization.
Common Questions
How do I calculate CPI?
Divide attributed media spend by attributed installs for the same cohort and currency. Include fees consistently. Spend of $10,000 and 5,000 installs gives $2 CPI (illustrative).
What revenue should I enter for D0, D7 and D30?
Enter cumulative revenue from the same paid-install cohort, not daily totals or revenue from all users. Use net revenue if you want fees and refunds reflected. Cohorts must be mature enough for each window.
Can eCPM be calculated without impressions?
IPM equals installs per thousand impressions. With IPM, eCPM equals CPI multiplied by IPM. Without IPM, an entered CPM is shown as an assumption, not a measured result. Leave both blank when unavailable.
How accurate is the payback estimate?
This is a scenario, not a forecast. It linearly interpolates cumulative revenue at D0, D7 and D30, and extrapolates the D7–D30 daily revenue slope beyond D30. Real cohort revenue usually decays; flat revenue produces no estimate.
Are my calculator inputs stored?
Calculation runs in your browser. Sharing includes numeric inputs in the URL, which recipients and web servers can see. Never use confidential inputs in a shared link. No names or email addresses are included.
Next Step
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