Sample Size Calculator
Determine how many people you need to survey to achieve your desired confidence and accuracy.
Sample Size Formula
For large populations: n = (z² × p × (1-p)) / E² where z = z-score (95% → 1.96), p = expected proportion (use 0.5 for max), E = margin of error. For finite population N, apply correction: n_adj = n / (1 + (n-1)/N).
Survey Parameters
Confidence Level
Margin of Error (%)
Population Proportion (p)
Population Size (0 for unknown/large)
Result
Required Sample Size
385
Z-Score
1.960
Recommended (round up)
385
For 95% CI with ±5% margin and p=0.5, you need 385 responses.