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Confidence Interval for a Proportion Calculator

Wald CI for a sample proportion.

Compute a normal-approximation (Wald) confidence interval for a sample proportion, given the sample proportion p̂, the sample size n, and the z critical value (default 1.96 for 95%).

Daniel Oh By Daniel Oh
Published Last reviewed 1 min read

Inputs

Results

Enter values and click Calculate to see 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

CI = p̂ ± z · √(p̂(1 − p̂) / n).

In depth

Compute a normal-approximation (Wald) confidence interval for a sample proportion, given the sample proportion p̂, the sample size n, and the z critical value (default 1.96 for 95%).