How much data do I need for my trip? This is a difficult question to answer but, here is a guide to help you to estimate how much data certain apps such as WhatsApp and Google Maps use, which are two of the more popular apps for the international traveler.
One way you can estimate your usage is to see how much data you typically consume back home. Contact your carrier and ask them what your average data consumption has been for the last 2-3 months. Don't forget that these are monthly usage quantities, hence, assuming that you use 5 GB a month during a typical month and your trip is 2 weeks, and your consumption is basically the same, you will be consuming about 2.5GB of data for your trip. Of course, you may need to consider other factors. For example, if you rent a car and will be using GPS on an every day basis, then you need to consider that.
In addition, you may use the below Data Usage Calculator. Remember, these are rough estimates because it is difficult to determine such things such as the quality of the video you may be watching, if your emails have attachments or not or if your WhatsApp usage is video or only calls. Still, this tool should give you a general idea of how much data you will need for your trip.