This calculator requires the use of Javascript enabled and capable browsers. This calculator is designed to derive the standard deviation of a set of entered numbers. Begin by entering the numeric values into the new number input box. Please be sure to click on the "Enter Number" button after each entry; the cursor will return to the new number entry box to prepare for the next value entry. There is no reasonable limitation as to the number of entries as long as you follow each entry by clicking on the "Enter Number" button. The number you entered will be placed in the running total for entries and into the box below for display of your entries. After the last value has been entered, click on the "Calculate Data" button for the returned calculated values of the entered data and the number of values entered, as well as the standard deviation and other displayed data. Actually, you can click on "Calculate Data" as often as you wish and it will average the entries up to that point and allow you to continue. Information displayed and updated with each click of "Calculate Data" is the last number entered in the session, the number of entries in the session, the sum of the entries, the mean average of the entries and the standard deviation. Clicking the "Clear Values" button will clear all the accumulators and allow you to start over. Clicking on "Clear Entry" will clear only that transaction. We also have a similar tool, the Virtual Average Calculator, available for use.

Standard deviation (as opposed to a standard deviate...) is defined as a measure of a frequency distribution's variability. The greater the variability, the larger the value of the standard deviation. To obtain the standard deviation, one must calculate the difference between the value of each individual item in the set population and also calculate the population mean, square these differences, add them, divide the sum by the total number of items, and finally, extract the square root.