Sample Size and Power Calculators
Sample Size for Proportion Calculator
Sample Size for Proportion Calculator estimate sample size for a proportion.
Sample Size and Power Calculators
Sample Size for Proportion Calculator
Estimate sample size for a proportion.
Formula
Single-proportion sample size: n = z^2 * p * (1 - p) / margin^2, rounded up.
About the Sample Size for Proportion Calculator
Estimate sample size for a proportion. Planning calculators connect effect size, precision, alpha, power, group count, and sample size for the specific design shown.
How the Sample Size for Proportion Calculator Works
Single-proportion sample size: n = z^2 * p * (1 - p) / margin^2, rounded up.
The calculation runs in your browser. Submitted values are validated for the required numeric range, data shape, units, and method-specific restrictions before a result is shown.
Required Inputs
- Margin of error as decimal (required)
- Planning proportion (required)
- Alpha (required)
Results Reported
The result panel shows the final answer together with the intermediate quantities needed to audit the calculation. Depending on this method, reported values include:
methodmargin_of_errorplanning_proportionalphaconfidence_levelz_criticalunrounded_sample_sizerequired_sample_size
Sample Size for Proportion Calculator Example
Use the example data button to load a known sample, then calculate and review the statistic, p-value or estimate, and interpretation.
| Input | Example value |
|---|---|
| Margin of error as decimal | 0.05 |
| Planning proportion | 0.5 |
| Alpha | 0.05 |
How to Use the Calculator
- Confirm that the calculator title and method match the quantity, test, conversion, or planning question you need to solve.
- Enter values with compatible units and the requested sample, group, matrix, count, date, or option format.
- Select Example Data to inspect a valid input layout, or enter your own values and select Calculate.
- Review the result table, formula, worked substitutions, warnings, and interpretation rather than using only the headline number.
- Use Copy Result or Download CSV when you need a reusable record of the displayed calculation.
Understanding the Result
Planning assumptions should be justified before data collection; attrition, clustering, unequal allocation, and multiplicity may require a larger design.
Keep the entered values, units, selected options, and any warning shown beside the result. For a hypothesis test, report the statistic, degrees of freedom where applicable, p-value, alpha level, effect size, and decision. For an estimate or conversion, report the formula convention and final unit.
Accuracy and Limitations
The calculator keeps full browser precision during calculation and rounds only for display. Accuracy still depends on correct inputs and on whether the displayed model represents the real problem. Educational calculators cannot replace required professional review, current official rules, field measurements, laboratory methods, or specialist statistical software where those are necessary.
Frequently Asked Questions
What does the Sample Size for Proportion Calculator calculate?
Estimate sample size for a proportion.
Which formula does the Sample Size for Proportion Calculator use?
Single-proportion sample size: n = z^2 * p * (1 - p) / margin^2, rounded up.
What input does this calculator need?
The calculator form shows the required values and validates them before calculating.
Are the formulas visible?
Yes. Each calculator displays its method, assumptions, and interpretation unless disabled by the site administrator.