Sample Size Calculator
Find the survey sample size you need from population, confidence level, and margin of error.
How it works
Before running a survey, this answers the essential question: how many responses do you actually need? It works from your population size, chosen confidence level, and acceptable margin of error.
The math uses the standard z-scores for 90, 95, and 99 percent confidence and applies the finite population correction, so a small population does not demand an unrealistically large sample.
Tightening the margin of error or raising confidence both push the required sample up — often faster than people expect, which is exactly why checking beforehand saves wasted effort.
Frequently asked questions
What margin of error should I use?
Five percent is a common default for general surveys. A smaller margin gives more precise results but requires a noticeably larger sample.
What does confidence level mean?
It is how sure you want to be that the true value falls within your margin of error. 95 percent is standard; 99 percent is stricter and needs a bigger sample.
Why does population size matter?
For small populations, the finite population correction lowers the sample you need. For very large populations, the required sample barely changes past a point.