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Survey sample size calculator
How many respondents do you actually need? Set your parameters for an instant, statistically sound answer. No signup, no spreadsheet.
±1% (high precision)±10% (exploratory)
You need at least
385
respondents for 95% confidence with a ±5% margin of error (unknown or very large population)
Uses Cochran's formula with the conservative p = 0.5 assumption, plus finite population correction where it applies. It is the standard textbook formula, so you can check it by hand.
Quick reference: 95% confidence, ±5% margin
| Population | Sample needed |
|---|---|
| 500 | 218 |
| 1,000 | 278 |
| 5,000 | 357 |
| 10,000 | 370 |
| 50,000 | 382 |
| 100,000 | 383 |
| Unknown or large | 385 |
Now weight and test your data.
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