Standard Deviation and Variance Calculator. This simple tool will calculate the variance and standard deviation of a set of data. Simply enter your data into the textbox below, either one score per line or as a comma delimited list, and then press "Calculate". Note: If you want to calculate the pooled variance of two samples, then you can use our pooled variance calculator. The calculator above computes population standard deviation and sample standard deviation, as well as confidence interval approximations. Population Standard Deviation The population standard deviation, the standard definition of σ , is used when an entire population can be measured, and is the square root of the variance of a given data set.