Root mean square or quadratic mean is used when the dataset has both positive and negative values or if the data vary continuously. To calculate the root mean square of a dataset, begin by squaring up all the given values. Then, add these squared values and divide them by the total number of data values to get the arithmetic mean. The square root of this value is the root mean square of the data. It is important to note that the root mean square is always equal to or greater than the arithmetic mean of the data values. Using a derived formula, root mean square can help find the RMS voltage in AC circuits, where the voltage cycles between positive and negative values. First, find out the peak voltage of the AC circuit and then divide it by the square root of two to obtain the value of RMS voltage.