Calculator
Sample Size Calculator
Calculate required sample size for surveys, A/B tests, and hypothesis tests.
⚡Quick Presets
📊Calculator
Required Sample Size
370
📖Understanding the Inputs
- Population Size: Total number of people in your target group. For very large populations (>100K), sample size barely changes.
- Margin of Error: How much the sample result may differ from the true value. ±5% is standard.
- Confidence Level: How certain you want to be that the true value falls within the margin. 95% is most common.
- Statistical Power: Probability of detecting a true effect. 80% is standard; clinical trials often use 90%.
- Minimum Detectable Effect: The smallest change you want to be able to detect (e.g., 1 percentage point lift in conversion).