# The Sample Size Calculator - Population Proportion

This calculator helps you find the appropriate sample size for estimating the proportion of a population that has a particular property within a specified margin of error.

You need to provide the confidence interval, the margin of error, and the sample proportion (%) below and click the ‘Calculate’ button:

Usually 90%, 95%, or 99%
Use 50% if you're not sure

Recommended sample size: 385

The confidence interval is usually 90%, 95%, or 99%. If you don’t know the sample proportion, leave it as 50%.

The formula to calculate the sample size is:

``````n = p*(1-p)*(Zα/2/E)2
``````

Where `n` is the sample size, `p` is the sample proportion, `Zα/2` is the z critical value, and `E` is the margin of error.

I hope this calculator is useful. Happy analyzing!

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