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Sample Size Calculator

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Estimate survey sample size from confidence level, margin of error, and optional population size.

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Confidence level

Cochran formula with optional finite-population correction.

Sample size

Recommended n
385
z-score1.96
Unlimited population n385

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How to Use

  1. 1 Pick 90/95/99% confidence
  2. 2 Set margin of error %
  3. 3 Leave proportion at 50% if unknown
  4. 4 Optionally enter finite population size

Features

  • Cochran formula
  • Finite population correction
  • z = 1.645 / 1.96 / 2.576
  • Client-side

Why it Matters

Researchers need a quick n before fielding a survey without opening a stats package.

★★★★★

Uses the standard Cochran sample-size formula with optional finite-population correction.

Frequently Asked Questions

Why 50% proportion?
It maximizes required n — safest when you do not know the true share.
Is this a power analysis?
No — this is a proportion survey sample-size estimate, not an A/B test power calc.
Advice?
Educational estimate only.
📖

Want to understand the math?

Browse all guides →
Size a Survey Sample for 95% C
sample size

Size a Survey Sample for 95% Confidence

Pick n for a survey at 95% confidence with a chosen margin of error.

16 Aug 2026

5 min read

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