A/B Test Sample Size Calculator

Estimate A/B test sample size and test duration from baseline conversion, lift, confidence and power.

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This calculator estimates the sample size needed per variant for a two-proportion A/B test. Enter your baseline conversion rate, minimum detectable lift, confidence level, statistical power and traffic pace.

What the result means

The output gives sample size per variant, total sample size and estimated days at your current traffic volume. It is meant for planning whether an experiment is realistically measurable.

Scope

The estimate uses a standard normal approximation for equal-sized variants and binary conversion outcomes. It is not a substitute for experiment design review when revenue, repeated users or sequential testing matter.