Data used when streaming radio app

Hello

I like to listen to the "KCSM Jazz 91" on my iPhone 5 (great jazz music, and I don't have any financial interest in it), but I'm wondering how much data a typical app like this uses. I've been listening to it only when I'm using WiFi, but would like to when I'm out and about and using my cellular data, which is limited.

I know, I could just listen for an hour and check the amount of data used, but it's much more fun asking fine people like you!

Thanks for your help.