Sample Size Calculator
How to Use
  • Set your confidence level
  • Enter margin of error
  • Provide estimated proportion
  • Add population size (optional)
  • Click Calculate
Quick Tips
Default values (95% confidence, 5% margin, 50% proportion) give the most conservative estimate (384 samples for infinite population).
Z-Score Reference
Confidence Level Z-Score
80% 1.282
85% 1.440
90% 1.645
95% 1.960
99% 2.576

Sample Size Calculator

Determine how many respondents you need for statistically significant results in your survey or study.

Sample size refers to the number of observations or responses you collect in your study. It's crucial because:

  • Too small: Results may not be statistically significant or representative
  • Too large: Wastes resources without meaningful improvement in accuracy

This calculator helps you find the "Goldilocks zone" - just right for your needs.

When unsure about the population proportion (p̂), use 50% (0.5). This is the most conservative estimate that gives the largest possible sample size for your confidence level and margin of error.

If you have prior data or estimates, using those values will typically yield a smaller (more efficient) required sample size.

Use the finite population correction when your sample size represents more than 5% of your total population. This adjustment reduces the required sample size when sampling from a small population.

For example, if surveying employees in a 500-person company, you'd use the correction. For national political polling, you typically wouldn't.

Real-World Examples