Avast! Pro on multiple platforms?

I have avast on multple platforms, an android phone and an ipad mini, will a licence apply for both of them or do i have to purchase a different licence for each?

The multiple platforms you mentioned will be using different versions of avast, so I would say you would need a license/registration for both.

Avast Pro is usually on the Windows Platform and is generally a single PC license unless you purchase a multiple PC license (3, etc.), but these licenses would only apply to the avast version installed on that platform.

There is no av version from avast for a Ipad.
IOS is not (yet?) supported.

You will need a license for each version.

Example:
1 pc (windows or mac) and 1 phone
You will need 2 licenses.
1 for the windows/mac software and one for the android software.