Formula To Convert Massive Quantities Of Cells Formatted In Hh:mm:ss To Seconds

Say I have a worksheet that has a column in which every cell is formated in hh:mm:ss format. The column is probably 100 cells long...so from A2 to A101 (A1 is the title of the column). Now, we need to take the data in cells A2:A101 and graph it, but the data needs to be formatted in only seconds. So, in column B, we want to convert the data from column A into seconds format.

For example,

cell A2: 00:01:46
cell B2: 106

Of course, we can't convert each cell by hand, because this needs to be done on a lot of data...worksheets upon worksheets.