Sample Size Calculator
Calculate the required sample size for your survey or study.
Determine how many responses you need for reliable results at your desired confidence level.
Required Sample Size
Sample Size Formula (for proportions):
n = (z² × p × (1-p)) / e²
With finite population correction:
n_adj = n / (1 + (n - 1) / N)
Where:
- n = required sample size
- z = critical value for the confidence level
- p = estimated proportion (use 0.5 if unknown — gives the largest sample size)
- e = margin of error (e.g., 0.05 for ±5%)
- N = total population size (optional)
Quick reference:
- For ±5% margin at 95% confidence: ~385 responses
- For ±3% margin at 95% confidence: ~1,068 responses
- For ±1% margin at 95% confidence: ~9,604 responses