Sample Size Calculator

Calculate the required sample size for a survey or study with desired confidence level, margin of error, and population size.

Confidence Level (%)

Margin of Error (%)

Population Size (optional)

Estimated Proportion (p) (0–1, optional)

Required Sample Size:

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About Sample Size

Sample size is the number of observations or respondents needed to estimate the true population parameter with a certain confidence level and margin of error.

How It Works

The calculator uses the standard formula for sample size with a finite population correction if population size is provided. By default, it assumes a proportion of 0.5 for maximum variability.

Advice

Use realistic population estimates when possible. For unknown populations, the tool defaults to an infinite population assumption. Always round up the sample size to ensure statistical validity.

FAQs

What if population is unknown? Leave the population field empty.
What is proportion (p)? It's the estimated response rate or characteristic proportion; default 0.5 gives max sample size.
Can margin of error be below 1%? Yes, but smaller margins require larger samples.