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Confidence Interval Calculator for Proportions

This calculator is used to find the confidence interval (or accuracy) of a proportion given a survey´s sample size and results, for a chosen confidence level.

How To Interpret The Results

For example, suppose you carried out a survey with 200 respondents. If 45% of respondents answered the question of interest in a particular way and your desired confidence level was 95%, the corresponding confidence interval would be ± 6.9%. That is to say that you can be 95% certain that the true population proportion falls within the range of 38.1% to 51.9%.



Sample Size

The number of respondents who answered the question.


Observed Proportion

The percentage of respondents who gave the response you are interested in.


Confidence Level

The degree of confidence in whether or not the true figure for the population lies within the confidence interval for the survey.

For example, a 95% confidence level indicates there is a 1 in 20 (5%) chance that the true population result falls outside the confidence interval range.


Please fill in the input fields above.