Statistics

Sample Size Calculator

Estimate how many responses or observations you need for a target confidence level and margin of error.

Preparing Sample Size Calculator

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Input

Enter the confidence level, margin of error, and estimated proportion to calculate the recommended sample size. You will see the result first and the step-by-step solution below.

Input summary

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Step by Step Calculation

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Calculate first and the full working will appear below automatically.

How to use Sample Size Calculator

Set the confidence level and precision you want, and the calculator will estimate how large the sample should be.

What this calculator is for

This calculator is for surveys, polls, A/B testing plans, and early study design when you need a sensible sample size before collecting data.

Tips

A smaller margin of error usually requires a larger sample.
If you do not know the expected proportion, 50% is often used as a conservative planning value.
Population size matters most when the full population is limited rather than extremely large.