Calculate exactly how many survey responses you need for statistically significant results. Supports finite population correction.

Use 50% if unsure (this gives the maximum sample size).

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    This calculation runs locally in your browser. View Source

    How to Use This Calculator

    Understanding the Results

    In statistics, the “Sample Size” is the number of individual responses you need to collect to ensure that your survey results accurately represent the overall population within your chosen margin of error.

    Key Concepts:

    • Confidence Level: How sure you want to be that the actual data falls within your margin of error. 95% is the industry standard.
    • Margin of Error: The wiggle room you allow. If your survey says 60% of people like pizza with a 5% margin of error, the “true” number is between 55% and 65%.
    • Population: If you are surveying a specific small group (e.g., “Employees at my company of 500 people”), input that number. If you are surveying “US Consumers,” leave it blank (infinite).

    The Math Behind It

    The tool uses Cochran’s Sample Size Formula with a Finite Population Correction:

    $$ n = \frac{\frac{Z^2 \cdot p(1-p)}{e^2}}{1 + \frac{\frac{Z^2 \cdot p(1-p)}{e^2} - 1}{N}} $$

    Where:

    • $n$ is the Sample Size needed.
    • $N$ is the Population Size.
    • $Z$ is the Z-score (1.96 for 95% confidence).
    • $p$ is the Estimated Proportion (0.5 yields the most conservative sample).
    • $e$ is the Margin of Error (decimal format).