Margin of Error Calculator
Enter the sample standard deviation, sample size and desired confidence level to calculate the margin of error.
Margin of Error Calculator
Calculate the margin of error for a sample mean at a chosen confidence level.
This calculator provides an estimate for general informational purposes only. It is not a substitute for professional financial, mechanical or engineering advice.
Margin of error quantifies the uncertainty around a sample estimate, calculated from the sample's standard deviation, its size, and a z-score corresponding to the desired confidence level.
Example
- With the default values shown above, this calculator returns: Margin of Error ≈ 2.94.
Frequently Asked Questions
What is the formula?
Margin of Error = z-score × (Standard Deviation ÷ √Sample Size), where the z-score corresponds to your chosen confidence level (1.96 for 95%, for example).
How does sample size affect margin of error?
Margin of error shrinks with the square root of the sample size, so quadrupling your sample size only halves the margin of error.