A/B Test Sample Size Calculator
Calculate required sample size for statistically significant A/B tests
Required Sample Size
Per Variant
3,839
Total
7,678
Test Parameters
Minimum Detectable Effect
20.0%
Statistical Power
80.0%
Significance Level
95.0%
How It Works
- Enter your baseline conversion rate
- Specify the minimum improvement you want to detect
- Adjust statistical parameters (confidence level, power). The default values of 95% and 80% are recommended and suitable in many cases.
- Get required sample size per variant
Understanding the Results
The calculator provides:
- Required sample size per variant
- Total sample size needed
- Statistical power analysis
- Confidence interval calculations
Statistical Parameters
- Significance Level: Default 95% confidence (α = 0.05)
- Statistical Power: Default 80% (β = 0.2)
- Effect Size: Your minimum detectable effect
Common Use Cases
- Website Optimization: Test new layouts, CTAs, or content
- Pricing Tests: Compare conversion rates between pricing plans
- Feature Launches: Test new features with a subset of users
Limitations
- Assumes normal distribution
- Requires stable baseline metrics
- Does not account for seasonal variations
- Best for binary outcomes (conversion/no-conversion)
Tips for Success
- Choose Realistic Effects: Smaller effects require larger sample sizes
- Consider Traffic: Factor in your daily/monthly traffic volume
- Account for Variations: Add buffer for unexpected fluctuations
- Run Full Duration: Don't stop tests early based on initial results