Sample Size Calculator
Result
Required Sample Size385
Margin of Error± 5%
Z-Score1.96
Proportion50%
↗ Math
Sample Size Calculator — free online calculator.
Formula
n = (z / E)² × p × (1−p) where E = margin/100
- Sample Size Calculator calculates its result from Principal, Z, Margin. It uses the formula n = (z / E)² × p × (1−p) where E = margin/100. Change any input to recalculate the result instantly.
- The main inputs are Margin of Error, Confidence Level, Estimated Proportion. Enter them in the units and format shown in the calculator.
- Keep comparable quantities in compatible units whenever the formula combines or compares them.
- Changing any input above recalculates the result with the same calculation engine used by this page.
Example: Sample Size
Inputs
- Margin of Error: 5
- Confidence Level: 95%
- Estimated Proportion: 0.5
Using Principal = 2, Z = 3, Margin = 4, the calculated result is 0.04.
Sample result: Calculating…
Frequently asked questions
What does the Sample Size calculate?
Sample Size Calculator — free online calculator.
Which values should I enter?
Enter Margin of Error, Confidence Level, Estimated Proportion using the units and format shown beside each field.
What formula does this calculator use?
The calculator uses the following relationship: n = (z / E)² × p × (1−p) where E = margin/100.
Why might my result differ from another source?
Results can differ when another source uses different units, rounding rules, conventions or assumptions. Compare the inputs and definitions before comparing results.
Does the result update automatically?
Yes. Changing an input updates the result using the same calculation engine shown on this page.