Work out how many people you need to survey for results you can trust. Choose a confidence level, set the margin of error you can tolerate, and enter the expected response proportion, which defaults to 50 percent for the most conservative estimate. The tool applies the standard sample size formula, z squared times p times one minus p divided by the margin squared, then applies a finite population correction when you supply a population size. Tightening the margin of error or raising the confidence level both increase the sample you need, sometimes sharply. This is exactly what pollsters, product researchers, and quality teams use to plan a study before collecting a single response. Everything runs locally in your browser, so nothing you enter is uploaded anywhere.
It gives the number of survey responses needed to hit your chosen margin of error at your confidence level.
A smaller margin of error requires a larger sample, since tighter precision needs more responses.
For small populations the tool applies a finite population correction, which lowers the required sample.
Work out how many people you need to survey for results you can trust. Choose a confidence level, set the margin of error you can tolerate, and enter the expected response proportion, which defaults to 50 percent for the most conservative estimate.
Yes. Sample Size Calculator is completely free, with no sign-up and no usage limits.
Yes. Sample Size Calculator runs in any modern web browser. There is nothing to download or install.
Yes. Sample Size Calculator runs entirely on your device in your browser, so nothing you enter is uploaded to a server.