按你的旅行方式来选流量大小

There is no single figure, because it follows your habits more than the length of the trip. The closest answer comes from your phone's own mobile-data counter: take a normal day, raise it for the extra maps and searching, lower it for what the hotel Wi-Fi will absorb, and multiply by the days you truly need data, the departure day included.

Most often it is the things that run without being asked: photo and video backup, app and system updates, and autoplay video in social feeds. Open the per-app usage screen on your device, which normally names the culprit at once. Where that screen sits differs by manufacturer and OS version.

It depends on how easy a correction would be on the road. If the plan tops up and you know how, sizing close to reality and topping up when needed usually costs less, since unused data is generally not refunded. If you will be somewhere buying again is difficult, or the trip contains a day that cannot be missed, the larger margin is a reasonable trade.

Not by headcount alone, because devices behave very differently. A laptop can pull large updates by itself the moment it sees internet, while a child's tablet goes almost entirely on video. Estimate device by device according to what each will actually do, and mark the shared network as metered if the operating system supports it.

It depends on your habits. For heavy daily use, or use you genuinely cannot predict, the peace of mind can be worth the premium. For light use spent mostly on Wi-Fi it is usually overpaying. Either way, read that plan's full-speed terms first, because the experience past the cap is noticeably different from the experience before it.

Plans are sold as a package of volume and validity, and the remainder is generally not refunded. Size closer to reality and top up if needed.

It depends on your habits. Heavy daily use can justify it, but always check the full-speed cap, since the experience past it differs considerably.