How to Calculate Age in Excel Using a Date of Birth

1. Open a new Microsoft Excel 2010 worksheet.
2. Click on cell A1. Enter the birth date of the person whose age you want to know. You can enter a date with dashes between the numbers, such as '3-30-1983.'
3. Click on cell B1 and enter this formula:=datedif(A1,today(),'y')In this example, 'A1' refers to the cell where you typed in the person's birth date. 'Today()' calls the current date on the machine. 'Y' indicates that Excel should give the result in years. Press 'Enter' on your keyboard to complete the formula entry, and the person's age will appear in cell B1.