How much data
How much do you actually need?
Nobody knows what a gigabyte looks like. Tell us where you are going, for how long, and roughly what you do on your phone — this works out the size and shows you the plan.
These are estimates, and deliberately generous ones: overshooting costs a couple of dollars, running out costs you your maps in a city you do not know. Video and long scrolling sessions mostly happen on hotel wifi, so the defaults describe a day on mobile data only.