We often wonder how much data does a FaceTime call over 3G consume.
Therefore, the team at 9To5Mac have actually conducted a test to solve
your this question. They put together two iPhone 4s to the test, one
running FaceTime over 3G, and took before and after screenshots of the
data. It was consuming around three megabytes a minute.
Now the test was conducted around for 5 minutes, and in total it used
14.7 MB of data. As said, it came out at an average of 3MB per minute.
The test was conducted “with lots of movement” on a jailbroken iPhone 4.
So if you are regular are making video calls, it can add up quickly.
However, making calls once in a while can be reasonable enough for you.