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Calculate the perfect sample size for your research with our free online calculator. Get accurate results with confidence levels, margin of error, and population size.
Total number of individuals in your population
How confident you want to be in your results
Acceptable range of error (typically 3-10%)
Expected proportion (use 50% for maximum variability)
A sample size calculator is a statistical tool that helps researchers determine the optimal number of participants or observations needed for a study to achieve reliable and valid results. It considers factors like confidence level, margin of error, population size, and expected proportion to calculate the minimum sample size required.
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Select whether your population size is known (finite) or unknown (infinite). For small, defined groups like employees or students, choose "Known Population". For large or undefined groups like "all internet users", choose "Unknown Population".
If you selected "Known Population", enter the total number of individuals in your target population. This helps optimize your sample size through finite population correction.
Choose how confident you want to be in your results. 95% is standard for most research. Use 99% for high-stakes decisions or medical research. 90% is acceptable for exploratory studies.
Enter your acceptable error range. Smaller margins (3%) require larger samples but give more precise results. Larger margins (10%) need fewer participants but are less precise. 5% is the most common choice.
If you know the expected proportion from previous studies, enter it. If unsure, use 50% as it provides the maximum sample size (most conservative approach).
Click "Calculate Sample Size" to see your results. Review the step-by-step explanation to understand how the calculation was performed. Consider the non-response rate adjustment for practical planning.
This calculator implements the Cochran formula (1977) for sample size determination, a peer-reviewed statistical method taught in research methodology courses at universities worldwide. The formula n = (ZĀ² Ć p Ć (1-p)) / EĀ² is the standard approach recommended by the American Statistical Association and used in published research across disciplines including medicine, social sciences, and market research.
Our calculations are based on established statistical principles documented in "Statistical Power Analysis for the Behavioral Sciences" (Cohen, 1988) and "Survey Sampling" (Kish, 1965). The formulas produce identical results to statistical software packages when given the same parameters. We follow ISO 20252:2019 standards for market, opinion and social research.
This tool is designed for educational and research planning purposes. It helps students, researchers, and professionals understand sample size requirements for their studies. For critical research decisions, we recommend consulting with a qualified statistician or research methodologist who can consider your specific study design and constraints.
All calculations are performed locally in your browser. We don't collect, store, or transmit your data. No registration required, no tracking cookies, complete privacy. Your research parameters and results remain confidential.
This calculator implements formulas from: Cochran, W.G. (1977) "Sampling Techniques" 3rd Edition; Krejcie & Morgan (1970) "Determining Sample Size for Research Activities"; and Yamane (1967) "Statistics: An Introductory Analysis". These are standard references cited in research methodology textbooks and used by institutional review boards (IRBs) for evaluating research proposals.