A/B Test Sample Size Calculator
Determine the sample size needed for your experiments with statistical confidence
Baseline Conversion Rate (BCR)
Current conversion rate of your control group
%
Minimum Detectable Effect (MDE)
Smallest change you want to detect (relative %)
%
Significance Level (α)
Probability of false positive (typically 0.05)
Statistical Power (1 - β)
Probability of detecting a real effect (typically 0.8)
Test Type
Two-sided tests for any change, one-sided for specific direction
Two-Sided
One-Sided
Traffic Split Ratio
Proportion of traffic to test group (0.5 = 50/50 split)
10%
50%
90%
Required Sample Size
Total Sample Size
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Control Group
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Test Group
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