Find the minimum sample size needed for your research or survey
This sample size calculator determines the minimum number of respondents needed for a survey or experiment to achieve statistically significant results. It uses the standard formula based on the normal approximation and optionally applies the finite population correction.
Where Z is the z-score for the confidence level, p is the estimated population proportion, and E is the margin of error (as a decimal). When population size N is provided, the finite population correction is applied: n_adj = n / (1 + (n-1)/N).
A proportion of 0.5 maximizes the required sample size, making it the most conservative estimate. When the actual proportion is unknown, using 0.5 ensures the sample size is large enough regardless of the true proportion.
A margin of error of 3-5% is common in social science research. Smaller margins of error require larger sample sizes. For most surveys, 5% provides a reasonable balance between accuracy and cost.