No DOB, only year of birth data is there in one column, need to calculate corresponding age in the other column based on today’s year/date.
3 Answers
Enter this in cell B2
and drag this down to other cells in column B
:
=IF(A1="", "", YEAR(NOW())A1)
Assumptions:
 The year of birth is in column A.
 Calculating the approximate age based only on the year.
 You want the approximate age displayed in column B.
 You want to leave the result blank if the corresponding year of birth is not entered.
Excel's formula for current year
=YEAR(TODAY())
To get your desired result, simply deduct the year of the DOB from the above formula to get the age of each individual.

How to do that deduction. Also, how to apply that logic for entire column (means multiple rows of data)? Sorry, I am a newbie to excel formulas. Commented Sep 23, 2016 at 15:23

Also I want the formula to leave the cell blank if year value is absent. Commented Sep 23, 2016 at 15:35
This is a nonaccurated approach but might help you:
Let´s say you have a column B named Date of birth, a column C named Today´s date and a column D named Result in years. To calculate the aproximated amount of years you need to subtract B from C in order to get an aproximated amount of days and convert this amount in years (365). For example, you have 10/10/1990 as date of birth and 23/09/2016 as today's date but if you subtract them you will get 9480 days that you will have to convert to years by dividing it for 365. The result is 25,97260, you could read this as almost 26 years and that's why this method is not completely accurate. Important: to get the total amount of days you will need to set the cell's format in Number or General.
Maybe this could help you. The procedure in Microsoft Excel 2010