What uses little
Text messaging, maps while navigating, bookings, tickets, weather: all of this weighs very little. A traveller sticking to these easily covers a week on a few GB.
What uses a lot
Video, in every form: social feeds that autoplay, streaming series, long video calls. Video is what empties a plan, not navigation.
Reference points, not promises
As a rough guide, for everyday use without streaming: 1 to 3 GB for a weekend, 5 GB for a week, 10 GB for two weeks, 20 GB for a month or for daily video. These are orders of magnitude, not a guarantee: no two travellers use the same amount.
The rule that matters
Turn off video autoplay in your apps, download offline maps before you go, and keep photo backups on the hotel Wi-Fi. Those three settings change your usage more than the plan you pick.
What happens if I use up my data?
The connection stops, with no overage billing. You can then buy a top-up from your account, without changing eSIM.
Should I take a large plan from the start?
Not necessarily. Start small: a top-up takes two minutes from your phone, whereas unused data is money spent for nothing.