Sample Size Calculator
Determine the required sample size for your survey or study. Calculate how many responses you need for statistically significant results.
Inputs
%
Results
Required Sample Size
385
Adjusted Sample Size385
Z-Score Used1.96
Effective Margin of Error4.99%
InterpretationYou need 385 responses for 95% confidence with ±5.0% margin of error.
How to Use This Calculator
- Enter the desired Confidence Level (e.g., 95%) and Margin of Error (e.g., 5%) for your survey.
- The calculator uses the formula n = z² × p(1−p) / e², where z is the critical z-score and p is the estimated proportion.
- If you have a prior estimate of the response proportion, enter it; otherwise use 0.5 (maximum variability, largest required sample).
- For a finite population, enter the Population Size and the calculator applies a finite population correction factor.
- A larger margin of error requires fewer respondents; halving the margin of error quadruples the required sample size.
- Results are rounded up to the nearest integer since you cannot survey a fraction of a person.
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Formula
n = (z² × p × (1-p)) / e²Related Calculators
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