Check how much data you are using now: On your iPhone, go to Settings - Mobile Data. If you're using an iPad, you might see Settings - Mobile Data. Scroll down to see which apps use cellular data. If you don't want an app to use your data, you can turn it off for that app. When mobile data is turned off, apps will only use Wi-Fi for data. To help you know how much you might need, we've included all the common data-consuming activities, with information on how many megabytes they actually use. 1 hour of Internet surfing 15MB 1 social media post with photo 350KB 1 minute of video streaming (standard) 2MB (120MB/hour) 1 minute of video streaming (HD) 5.1MB (306MB/hour) 1 minute of music streaming 500KB (30MB/hour) 1 email (without attachment) 20KB 1 email (with standard attachment) 300KB 1 downloaded application/game/song 4MB Notice: You can find several data calculators on the web. Depending on the data you have entered: the calculator will show approximate cellular data costs and values depending on the applications you plan to use and how often you use them during your trip.