Sample Size Calculator
Find how many survey responses you need for a chosen confidence level and margin of error — with the finite-population correction built in.
Required sample size
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Share of population —
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How it works
n = z²·0.25/e², corrected: n/(1 + (n−1)/N)Frequently Asked Questions
How many people do I need to survey?
For ±5% margin at 95% confidence, about 385 responses regardless of population size; ±3% needs about 1,068. Small populations need fewer thanks to the finite correction.
What do confidence level and margin of error mean?
95% confidence with ±5% margin means: if you repeated the survey many times, 95% of results would land within 5 points of the true population value.
Why doesn't a bigger population need a much bigger sample?
Statistical precision depends on the sample's own size, not the population's — sampling 400 people estimates a city and a country almost equally well once the population is large.