How much data will this use?

I have a iPhone 4 and I have the 3 GB plan, I have used 850 mb so far, how much data would it use to download a 90 mb app

90 Megabytes? Is it that hard to figure out?

Ok… 3GB = 3000MB 3000MB - 850MB - 90MB your left withe 2060

It might use a bit more, there's overhead, potential bad packets, a slight bit of data being uploaded too

3GB is actually 3072MB