Math & Science
Sample Size Calculator
Calculate required sample size for surveys
Formulas and edge cases are reviewed against authoritative references before publication. For methodology, editorial standards, or corrections, use the links below.
Frequently asked questions
Why use 50% proportion?
50% gives maximum variance, ensuring sample is large enough for any result.
Does population size matter?
Only for small populations. For populations over 20,000, effect is minimal.
What margin of error should I use?
5% is standard for most surveys. Lower margin requires larger sample.
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About this tool
This Sample Size Calculator turns your inputs into practical results. Provide Confidence Level, Margin of Error, and Population Size to calculate Required Sample Size and Formula Used.
Adjust values to compare scenarios and see how sensitive the result is. The calculation uses the numbers as entered, so double-check units and expect small differences from rounding in the displayed totals.