Free tool

Store test calculator

Enter a week of your own numbers to see how long a store test needs, and the smallest change your traffic can tell apart from chance.

Example numbers. Replace them with one week from your own reports.

StoreImpressions a weekDownloads a weekChange to detectVersions, the current one includedShare of visitors in the testConfidence

Showing a 20% change takes 5 weeks (31 days) at this traffic.

Conversion now: 3.00%. Each version needs about 10,958 impressions in a product page optimization test.

Within 90 days, the smallest change this traffic can show is about 11%.

A before-and-after read of four weeks on each side could, at best, show a change of about 15%. In practice it needs a larger change than that, because two stretches of weeks also differ for reasons that have nothing to do with the listing.

How this is calculated

The math is the standard sample size for comparing two rates, at 80% power, with the confidence you choose.
On the App Store, enter impressions and downloads. On Google Play, enter store listing visitors and installs.
A before-and-after read needs at least as much traffic as a test, and in practice more, because weeks also differ for other reasons.
Nothing is uploaded: the math runs in your browser.

Audit a listing free when you want the public listing checked, not only the character count.