For a typical 10-day Vietnam trip covering Hanoi, Ha Long Bay, Hoi An, and HCMC, 6 GB to 10 GB is enough for most travelers. A 2 to 3-week multi-city trip with daily Grab, Google Maps, WhatsApp, and casual photo uploads usually needs 10 GB to 20 GB. Heavy users uploading reels from Sapa or Ha Giang or working remotely should pick 20 GB or 100 GB. Long bus rides and train journeys consume more data than expected because of constant navigation and entertainment use.