Sample Size Calculator
Calculate the required sample size for any survey. Supports confidence interval adjustment and finite population correction.
Parameters
How much sampling error you can tolerate. 5% is the standard for most research.
Expected % answering 'yes' or selecting the option. Use 50% if unknown; this maximises required sample size.
Leave blank for infinite population. Enter total population size to apply finite population correction.
Required Sample Size
385
For infinite / large population
Actual Margin of Error
±5.0%
At 95% confidence with n=385
This gives the number of completed, usable responses. Add 15–25% to your outreach target to account for non-response and disqualifications.
Quick reference: 95% confidence, p=50%
| Margin of error | n (infinite pop.) | Typical use |
|---|---|---|
| ±1% | 9,604 | National polls, large-scale tracking |
| ±2% | 2,401 | Robust tracking studies |
| ±3% | 1,067 | Most quantitative research |
| ±5% | 384 | Standard market research |
| ±10% | 97 | Directional / exploratory studies |
Want the methodology behind this?
Read our full guide on sampling methods, covering study design, interpretation, and common mistakes.
Read the guide