Math Calculators

Sample Size Calculator

Estimate required sample size for a population proportion with chosen confidence and margin of error.

Confidence Level

Margin of Error (%)

Estimated Proportion p (%)

Population Size (optional)

Required Sample Size385

Infinite Population Size385

Sample Size Formula

n0 = z²×p(1−p)/e²

With finite population correction:

n = n0 / [1 + (n0−1)/N]

95% confidence, 5% margin, p=50% gives sample size about 385.

Why is p=50% common default?

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