Sample Size Calculator
Calculate the required sample size for surveys and experiments. Set confidence level, margin of error, and population size.
Based on 95% confidence, ±5% margin of error, 50% proportion, infinite population.
How to Use the Sample Size Calculator
Choose your confidence level (how sure you want to be), set your desired margin of error (how precise you need your results), and optionally enter your total population size. The calculator instantly shows the minimum number of responses you need.
What Is Confidence Level?
The confidence level tells you how often the true population value will fall within your margin of error if you repeated the survey. A 95% confidence level means that if you ran the same survey 100 times, 95 of those times the results would fall within your margin of error.
What Is Margin of Error?
The margin of error is the range of values above and below the actual result. For example, if 60% of respondents say "yes" with a ±5% margin of error, the true value is likely between 55% and 65%.
When to Use Population Proportion of 50%
If you don't know the expected proportion of your population that will choose a given answer, use 50%. This gives the largest (most conservative) sample size and guarantees your margin of error regardless of the actual result.