Work out multivariate test duration instantly with clear inputs, formula shown and shareable results.
Sample size scales with baseline variance and inversely with the square of the effect you want to detect, then multiplies by the number of variants. That is why adding variants to a low-traffic test makes it practically undetectable.
Sample size
Per variant ≈ 2 × 7.849 × p(1-p) / (p × MDE)² at 95% confidence and 80% power
Figures are estimates based on the inputs given. Marketing performance, platform fees and conversion behaviour vary by audience, channel and season. Use this as a planning guide, not a forecast.
Because sample size scales with the inverse square of the effect — halving the effect quadruples the traffic needed.
Yes, and ideally whole weeks, so weekday and weekend behaviour are both represented.