Quick facts
| What you are doing | Roughly per hour | A day of it |
|---|---|---|
| Maps with the area downloaded | Almost nothing | Almost nothing |
| Messaging and email | A few MB | Under 0.1 GB |
| Browsing and searching | 10 to 50 MB | 0.1 to 0.3 GB |
| Social feeds with autoplay | 100 to 300 MB | 0.5 to 1.5 GB |
| Music streaming | 40 to 150 MB | 0.3 to 1 GB |
| Video streaming | 0.3 GB at low quality, several GB at high | 1 GB and up |
| Video calls | 0.5 to 1.5 GB | Depends entirely on call length |
Disclosure: VietSIM sells prepaid eSIMs for Vietnam. The point of this page is to stop you buying more data than your trip needs.
The honest answer
Most visitors use 0.5 to 1 GB a day. That covers the things a trip actually runs on: directions, translating a menu, messaging whoever you are travelling with, looking up opening hours, booking a car, and putting a few photos online.
The number moves for three reasons, and only three:
- Video. Streaming anything is the single biggest line on the bill. Netflix publishes a data usage setting precisely because the difference between its quality levels is several times over, not a few percent.
- Video calls. A long call home costs about what streaming does.
- Sharing. Every phone or laptop on your hotspot spends what it would spend on its own.
Everything else is noise by comparison.
Cut the biggest cost before you go
Two settings, five minutes, and most of the risk disappears.
Download the map. Google Maps lets you download an area and navigate inside it with no connection at all. Do this for each city before you fly, on hotel Wi-Fi, and the part of your data you were most worried about stops counting.
Turn off automatic photo backup on mobile data. A week of holiday photos syncing in the background will outspend everything else you do. Let it run on Wi-Fi overnight instead.
If music matters to you, Spotify’s quality setting works the same way Netflix’s does, and downloading playlists before you travel removes that line too.
Work out your own number
The table above is an average, and averages are wrong for individuals. The calculator below takes your trip length, how you actually use a phone, and how many people will be on your hotspot, and shows what that adds up to. Its assumptions are printed underneath it so you can disagree with them.
Buying for it
Plans in Vietnam are usually sold either as a daily allowance that resets each morning, or as a single pot for the whole trip. A daily allowance suits steady use and forgives one heavy day. A pot suits a trip with one big day of uploads and a lot of quiet ones.
Which shape fits your trip is worked through in which eSIM for Vietnam fits your trip, and the plans currently on sale are in the Vietnam eSIM store. If you are still deciding whether you need a Vietnamese number alongside the data, that question has its own page.
Before you buy
- Download offline maps for every city on your route.
- Turn photo backup to Wi-Fi only.
- Count the people who will share your hotspot, not just yourself.
- Buy for your normal days, not your worst one: topping up is easy, and a plan you do not finish is money left on the table.