Use the transfer time tool to calculate how long it would take to download the latest movie from iTunes, or how long it would take to send a large PowerPoint presentation.
Just put in the size of the file(s) and the amount of bandwidth you have via DSL, CABLE, T1, wireless or Ethernet and you get your answer in real time. Adjust your speed and the tool will recalculate the changes on the fly.
Source:
http://ismashphone.com/2012/12/inetcalc-free-iphone-app.html