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About this tool
Estimate sample size using selected study assumptions.
Uses the normal-approximation proportion formula and optional finite population correction. It does not account for cluster design, nonresponse or complex sampling.
How survey sample size is calculated
This calculator estimates a sample size for a single population proportion using a confidence level, margin of error and expected proportion. An optional finite population correction is applied.
Worked example
With 95% confidence, a 5% margin of error and 50% expected proportion, the initial estimate is 385 respondents.
Frequently asked question
Does this account for nonresponse?
No. Increase the target sample size separately for nonresponse, clustering and other study design considerations.