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Sample Size Calculator

Work out how many respondents you need for a given confidence level, margin of error, and population size.

Daniel Oh By Daniel Oh
Reviewed by Dr. Helena Ortiz
Published Last reviewed 1 min read

Inputs

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Results

Enter values and click Calculate to see results.
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How to use this calculator

  1. Fill in the inputs above using the units you already have.
  2. Values update automatically as you type — no submit button needed.
  3. Hover any result row for the underlying formula and intermediate values.

Formula

n = (z² · p(1 − p)) / e², adjusted for a finite population: n' = n / (1 + (n − 1)/N).

In depth

Work out how many respondents you need for a given confidence level, margin of error, and population size.