Here is a step-by-step tutorial on how to calculate age in Excel:

1. Enter the date of birth into cell A2.
2. Enter the TODAY function into cell B2 to return today's date.
3. The DATEDIF function below calculates the age of a person in years: =DATEDIF(A2,B2,"Y")
4. If you want a more detailed age, you can have Excel calculate the exact age in years, months, and days. Use this formula: =DATEDIF(B2,TODAY(),"Y")&" Years, "&DATEDIF(B2,TODAY(),"YM")&" Months, "&DATEDIF(B2,TODAY(),"MD")&" Days".

That's it! You can now calculate the age of anyone using Excel.