Free Rowform tool

Free Sample Size Calculator

Estimate how many survey responses you need for a chosen confidence level and margin of error.

Rowform free toolPrivate · runs in your browser

How to Use This Sample Size Calculator

Enter the population size if it is known.
Choose a confidence level, margin of error, and expected distribution.
Use the recommended response count as a research planning target.

Why sample size matters

A sample should be large enough to represent the population without collecting more responses than the research needs. This calculator applies a finite population correction when you provide a population size.

The Formula

n = Z² × p(1-p) ÷ e²

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Frequently Asked Questions

What should I enter for expected distribution?

Use 50% when you are unsure. It represents maximum variability and produces the most conservative sample size.

What if I do not know the population size?

Leave it blank. The calculator will use the large-population result.