Just got an iphone 5 love to use skype how much can I get with 1gb?

I have family in america which I talk to and skype a lot! My iphone has 1gb of internet which is free and I'm not going to go over that. So how much does 1gb using skype? Like how much time does that give me on skype?

Well, It depends on your use but I'd say maybe 3-4 hours of video call.