Our calculator gives the percentage points of error either side of a result for a chosen sample size.
It is calculated at the standard 95% confidence level. Therefore we can be 95% confident that the sample result reflects the actual population result to within the margin of error. This calculator is based on a 50% result in a poll, which is where the margin of error is at its maximum.
This means that, according to the law of statistical probability, for 19 out of every 20 polls the 'true' result will be within the margin of error shown.