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Proportion Sample Size Calculator
Plan a normal-approximation sample size for a stated proportion precision.
Two-sided confidence (%), Expected proportion (0–1), Desired margin (percentage points), Population, Finite population size; ignored for infinite
JSON
Browser only
Runs locally in your browser. Your files, pasted content and generated output are not uploaded. Reset clears this tool’s working data.
This tool needs JavaScript. If it does not load, refresh the page and try again.
How to use this tool
- Enter the labelled values and use the displayed units.
- Choose Calculate result and inspect the full report, assumptions and undefined/no-solution status.
- Choose Download result to save the complete JSON. Reset clears results and restores the example controls.
Examples
Two-sided confidence (%): 95
Expected proportion (0–1): 0.5
Desired margin (percentage points): 5
Population: infinite
Finite population size; ignored for infinite: 10000
Limitations
- Confidence90/95/99%; expected proportion strictly0–1; margin percentage (0,100); infinite or finite population whole>=2. Round sample upward after finite-population correction. Assumes simple random sampling; no response/design effect or guarantee for rare/extreme outcomes.
- Scalar numeric inputs use explicit decimal syntax and IEEE-754 arithmetic; unless a tighter bound is stated, positive values are 1e-12–1e12 and nonnegative values 0–1e12. Derived inventory counts above 1 billion and nonfinite results are refused. Combined input limit400,000 UTF-8 bytes;complete JSON output limit4MiB. Numeric/code input controls allow128 characters. All processing stays in your browser.
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