Confidence Interval Calculator

Confidence Interval Calculator is an online tool for calculating the confidence interval, provided you give the standard deviation and mean. We calculate the confidence interval of the mean using the normal distribution or the student's t distribution, and the confidence interval of the standard deviation is calculated using the chi-squared distribution.

What does the confidence interval mean?

A confidence interval in statistics is a range of values established by using observed data and estimated at the desired confidence level that may contain the true value of the taken parameter. The confidence level, for example, a 95% confidence level, refers to how genuine the estimation technique is, rather than the degree of certainty that the computed confidence interval contains the true value of the parameter under consideration. Before computing the confidence interval, the desired confidence level is set. Then, it displays the proportion of confidence intervals that, when formed given the chosen confidence level over an unlimited number of independent trials, will contain the true value of the parameter.

How to use the Confidence Interval Calculator?

The following is how to use the confidence interval calculator:

Step 1: In each input area, provide the confidence level, sample size, standard deviation, and mean.

Step 2: Press the "Calculate" button to get the interval value.

Step 3: Finally, the confidence interval will be presented in the new window.


We know the sample statistics when we use sample data, but we don't know the true value of the population parameters. So instead, we can construct the confidence interval by treating the population parameters as random variables.

First, we must define the confidence level, the required level of certainty that the parameter's actual value will be inside the confidence interval. For example, a confidence level of 0.95 is widely used by researchers.

The calculator's confidence level is set to 95 by default, but you can adjust it. The results of this confidence interval calculator are presented in APA format.