Sample Size Calculator
The sample size needed for a survey at a given confidence and margin of error.
Result
Required sample size
385
How it works
n = z² · p(1−p) ÷ e²
This gives how many responses you need for a reliable survey. Use 50% proportion for the most conservative (largest) estimate when unsure.
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Frequently asked questions
Why use 50% proportion?
It gives the largest, safest sample size when you have no prior estimate of the result.
What margin of error is typical?
5% is common; a smaller margin needs a much larger sample.
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