Statistics

Sample Size Calculator

Plan your survey with confidence. Find the minimum sample size needed for a given confidence level, margin of error and expected proportion.

Confidence level

Margin of error (%)

Expected proportion p (%)

Population size (0 = unknown / large)

Cochran's formula: n₀ = z²p(1−p)/e², then finite-population correction n = n₀ / (1 + (n₀−1)/N).

Pick 90–99% confidence and any margin of error.

Apply the finite-population correction automatically.

Classic 95%/5% sizing table included below.

Z critical values computed on the fly.

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