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Margin of error for a proportion

Margin of error for a proportion: calculate a transparent estimate from the values and assumptions you provide.

Margin of error for a proportion: calculate a transparent estimate from the values and assumptions you provide.

Both dots and commas are accepted as decimal separators.

Your inputs stay in your browser. Displayed results are rounded to a maximum of 12 significant digits.

Method and assumptions

Method version 1.0.0 · Updated

Calculate

Formula: e = z √[p(1−p)/n] × 100

Margin of error for a proportion: calculate a transparent estimate from the values and assumptions you provide.

zScore
Z value for confidence level
sampleSize
Sample size
expectedProportion
Expected proportion (%)

Normal approximation; assumes random sampling and sufficiently many observations.

Calculate with code

These short examples use the same inputs and core calculation as this tool. Adapt validation and formatting to your application.

JavaScript
const margin = 1.96 * Math.sqrt(0.5 * 0.5 / 400); // 0.049