What confidence level should I use?

95% confidence level is most commonly used in research, meaning you can be 95% confident your results reflect the true population. Use 99% for more critical decisions (requires larger sample) or 90% when resources are limited.

What margin of error is acceptable?

A 5% margin of error is standard for most surveys. Use 3% for more precise results (requires larger sample) or up to 10% for exploratory research. The margin of error represents how much your results might differ from the true population value.

Why use 50% for expected proportion when unknown?

50% gives the maximum sample size needed because it represents the highest variability. If you expect a different proportion based on prior research, use that value to potentially reduce your required sample size.

How does population size affect sample size?

For large populations (>10,000), population size has minimal effect on required sample size. For smaller populations, you need a higher percentage of the population to achieve the same precision.

Sample Size Calculator – Statistical Sample Size

Calculate the required sample size for surveys and research studies. Determine statistically significant sample sizes based on confidence level, margin of error, and population size.

Sample Size Calculator – Statistical Sample Size

Calculate the required sample size for surveys and research studies. Determine statistically significant sample sizes based on confidence level, margin of error, and population size.

Population Size

Total population size (leave blank for infinite population)

Confidence Level*

Desired confidence level

Margin of Error (%)*

Acceptable margin of error (typically 3-5%)

Expected Proportion (%)*

Expected response proportion (use 50% if unknown)

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Understanding Sample Size Calculation

Sample size calculation determines how many participants you need in a study to achieve statistically reliable results. The right sample size balances statistical power with practical constraints like time and budget.

Key Factors Affecting Sample Size

Factors that influence required sample size:

Confidence Level: Higher confidence requires larger samples
Margin of Error: Smaller margins require larger samples
Population Variability: More diverse populations need larger samples
Population Size: Very large populations don't significantly affect sample size
Expected Response Rate: Account for non-responses in your planning

How to Use This Calculator

Follow these simple steps to get accurate results:

Enter your population size
Enter your confidence level
Enter your margin of error (%)
Enter your expected proportion (%)
Click the "Calculate" button to see your results
Review the detailed breakdown and explanation

Why Use Our Sample Size Calculator – Statistical Sample Size?

100% free and no registration required
Instant, accurate calculations with professional formulas
Mobile-friendly design that works on any device
Privacy-focused - your data never leaves your browser
Educational content to help you understand the results

Frequently Asked Questions

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