A/B Test Sample Size & Duration Calculator
alculate the sample size and test duration you need from baseline conversion, MDE, traffic, alpha, and power—so you test once with confidence.
Stop running underpowered tests. Enter your baseline conversion rate (e.g., 3%), the minimum detectable effect you care to find (e.g., +15%), your daily traffic per variant, and pick significance (α) and power (1–β).
We compute:
Required sample size per variant using a standard two-proportion z-test approximation.
Estimated test duration in days given your daily traffic.
Guidance on when to stop and common pitfalls (peeking, uneven traffic, seasonality).
Use this before spinning up a Play like Creative Testing to keep timelines realistic and stakeholders aligned.
