Margin of Error Calculator

Margin of Error Calculator

The Margin of Error Calculator is a helpful tool for estimating the margin of error associated with survey results. This tool allows you to determine the range within which the true population parameter is likely to fall based on a given sample size and confidence level.

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Enter the following information to calculate the margin of error:

Margin of Error:

How to Use the Calculator

Sample Size

  • Enter the size of the sample you’ve collected. The sample size is the number of observations or responses you have from your survey or study.

Confidence Level

  • Input the desired confidence level as a percentage. Common choices are 90%, 95%, or 99%, which represent the level of confidence you want in your estimation.

Population Size (Optional)

  • If you know the size of the entire population you’re sampling from, you can enter it here. This information is optional, but it can provide a more accurate margin of error calculation when available.


  • Click the “Calculate” button to perform the calculation. The calculator will use the sample size, confidence level, and population size (if provided) to estimate the margin of error.

Formula for Margin of Error Calculator

Margin of Error (MOE) Formula:

MOE = Z * √[(p * (1 – p)) / n]


  • MOE is the Margin of Error.
  • Z is the Z-score, which corresponds to the desired confidence level.
  • p is the estimated proportion (or success rate) of the population.
  • n is the sample size.

The Margin of Error is calculated by multiplying the Z-score by the square root of the product of the estimated proportion (p) and its complement (1 – p), divided by the sample size (n). This formula provides an estimate of the range within which the true population parameter is likely to fall with a certain level of confidence.

Interpretation of Results

The Margin of Error represents the range or interval within which the true population parameter is likely to fall. It is expressed as a percentage and can be used to understand the precision of your survey results. A smaller margin of error indicates a more precise estimate, while a larger margin of error suggests a less precise estimate.

Important Notes

  • The Margin of Error Calculator assumes a normal distribution for your data.
  • When the population size is much larger than the sample size (typically more than 20 times larger), you can often treat it as infinite.
  • For other confidence levels not provided in the calculator, you may need access to a more comprehensive Z-table or a statistical software program to obtain the corresponding Z-score.