Landing Page Conversion Calculator
With a significance check, so you stop peeking.
Lift from B
17.39%
significant at 95%
A z score of 1.98 clears the 95% threshold, so the difference is unlikely to be chance. Run the test to a planned end rather than stopping here — peeking at significance repeatedly is how false positives get shipped.
How the Landing Page Conversion Calculator works
Stopping a test the moment it looks like a winner is the single most common way A/B testing produces changes that do not replicate. A significance check tells you whether the difference could easily be noise — and at typical ecommerce volumes, it usually could.
Not financial advice. Marketplace fees change, and they vary by country, plan and seller status. Every rate here is an editable default, not a quoted price — check the platform's current fee schedule before you price a product against it. This is not tax or business advice.
Frequently asked questions
How do I know if a test result is real?
Compare the difference against its standard error. A z score above 1.96 corresponds to 95% confidence, which is the conventional threshold — not a guarantee.
Why is peeking a problem?
Because random fluctuation crosses the threshold temporarily. Checking repeatedly and stopping when it does turns a 5% false positive rate into something far higher.
How long should a test run?
To a sample size decided before it starts, and always in whole weeks to cover the weekly cycle. Stopping early on a good result is the most expensive habit in testing.
What if my traffic is too low to test?
Then test bold changes rather than small ones — a 20% effect needs a fraction of the traffic a 3% effect does. Low-traffic sites should redesign, not tune.