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Sample Size for a Mean Calculator

n = (z · σ / E)².

Compute the minimum sample size required to estimate a population mean within a target margin of error E at a chosen confidence level (z critical), given a population (or pilot) standard deviation σ: n = (z · σ / E)².

Daniel Oh By Daniel Oh
Published Last reviewed 1 min read

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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 = (z · σ / E)²

In depth

Compute the minimum sample size required to estimate a population mean within a target margin of error E at a chosen confidence level (z critical), given a population (or pilot) standard deviation σ: n = (z · σ / E)².