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LTV & payback calculator

For subscription apps: how much an install is worth over its lifetime, and which month a cohort pays back its CPI. Runs in your browser; nothing is sent anywhere.

Your funnel

Use realized numbers from your subscription platform, not platform-reported ones.

$

Spend ÷ installs for the channel you're evaluating.

%

Share of installs that ever become a paying subscriber. Trial starts don't count.

$

Annual plans: divide the annual price by 12.

%

30%, or 15% under small-business programs and after year one.

%

Share of paying subscribers who cancel each month.

Results

Payback

Never

Lifetime revenue per install never reaches CPI at these inputs.

Lifetime value per install

$3.50

After the store's cut. LTV:CAC 1.00x.

Cumulative revenue per install

D30

$0.28

0.08x ROAS

D90

$0.77

0.22x ROAS

D180

$1.38

0.39x ROAS

D365

$2.21

0.63x ROAS

Highlighted checkpoints have covered CPI. Average subscriber lifetime at this churn: 12.5 months.

Read it right

This is a model, not a measurement. Once a cohort is old enough, replace the D30 and D90 cells with realized numbers from your cohort matrix — the model is for deciding today, the matrix is for checking whether today's decision was right.

The model

Revenue per install, month n  = conversion × net price × (1 − churn)^(n−1)
Cumulative through month n    = conversion × net price × (1 − (1 − churn)^n) ÷ churn
Lifetime value per install    = conversion × net price ÷ churn
Payback month                 = first n where cumulative ≥ CPI

With a $3.50 CPI, 4% install-to-paid conversion, $9.99 monthly price, 30% commission, and 8% monthly churn, an install is worth about $3.50 over its lifetime — exactly break-even, with payback never quite arriving. Move conversion to 6% and payback lands in month 10. That sensitivity is the point: the payer rate is the lever, and it is a product and onboarding lever more than a media one.

Per install, not per payer

Subscription dashboards love LTV per paying customer because it is a big number. It is the wrong number for acquisition decisions: you paid for every install, including the 96% who never subscribe. Dividing by payers makes a channel with cheap, low-intent installs look identical to one with expensive, high-intent installs. Per-install LTV is what CPI can be compared to; the glossary entry on LTV covers the distinction.

Model first, then measure

Use this to decide whether a channel is worth testing and what CPI you can afford. Then let the cohort matrix take over: realized D30 and D90 revenue per install replaces the model's estimates as cohorts mature. The mechanics of reading that matrix, including the immature-cohort trap, are in D30 realized LTV from cohorts. For the margin side, see the break-even ROAS calculator.

Common questions

How is LTV calculated for a subscription app?
Per install: install-to-paid conversion rate × net monthly price ÷ monthly churn. That gives the average lifetime revenue an install generates after the store's cut. Per paying subscriber, drop the conversion rate — but that figure cannot be compared to CPI, because CPI buys installs, not payers.
What is CAC payback period?
The time until a cohort's cumulative revenue equals the spend that acquired it — the month where cohort ROAS crosses 1.0x. It turns the LTV:CAC ratio into a cash question: how long is money out before it comes back.
What is a good LTV:CAC ratio for mobile apps?
The SaaS rule of 3:1 is a starting point, not a law. What matters is the LTV window: a 3:1 ratio at D365 and a 0.6:1 ratio at D30 can describe the same healthy app. Decide the acceptable payback period from cash constraints, then back out the ratio.
Why does the calculator use monthly churn instead of retention curves?
Because monthly churn is the number subscription platforms report directly and most teams know. Real retention is not perfectly geometric — early churn is higher — so the model is optimistic in the first months and roughly right over the lifetime. Replace the D30 and D90 outputs with realized cohort numbers as soon as you have them.

Related terms: payback period, LTV:CAC, churn rate, trial conversion rate.