calculation of age

Webform is not capable of doing this without custom code, as far as I know. A quick Google turns up this answer: http://www.r2marketing.nl/blog/calculate-fields-webform-drupal

As mentioned in the submission guidelines:

Any issues regarding "how do I code ..." or "how do I theme ..." will not be answered. Please look elsewhere for coding resources.

So I'm marking this fixed (so it still shows up in the listing for a while), but this issue won't get more feedback from maintainers.

@Reema_0902 - You could also give this sandbox module a whirl. It works well with a use case as you describe: Webform Computed Component