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A/B Test Duration Calculator

Calculate how many days an A/B test needs to run to reach significance, by traffic and MDE.

CRO
Days to significance
52
~7.4 weeks
Sample size per variant
51,733
Total sessions needed
103,467
Assumes 50/50 split, 95% confidence, 80% power. Run tests for full week cycles to capture weekday/weekend variance.

About this tool

Given daily sessions split between control/variant and a target MDE, calculator estimates days needed for stat-sig results.

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