Hi there Mike1970,
This is a toughie.....I've done Google search for 'how much data will I use on Skype' and Skype support says the following:
Skype's answer
Then there's another thread online which gives a totally different view:
Independant answer
The Skype service is rather data hungry in my opinion as it's live streaming and will use much more data than say browsing a few web pages and checking email.
Because VOIP services such as Skype are yet to be supported on our network, then we're unable to quote specific data usage for a typical session.
I'll leave thip open to other users who may be able to offer further assistance.
Sorry,
LeeH
eForum Team