How much eSIM data do you actually need?
Most travellers buy too much or too little because “5 GB” means nothing until you know what a day abroad costs. Here is what your phone actually spends, what to pick for a trip your length, and what to do when you get it wrong.
The short version: maps and messaging sip data, video and hotspots gulp it. If you are between two sizes, take the smaller one — you can top up mid-trip in seconds, and unused data does not roll over.
What sips data
You could do these all day on a small plan and barely notice.
- Maps and navigation
- Messaging apps
- Email and web reading
- Music, if you stream it rather than download it
- Tickets, boarding passes, ride-hailing, translation
What gulps it
Any one of these can outspend a week of everything else.
- Video streaming — the single biggest line item
- Video calls
- Hotspot and tethering, especially to a laptop
- Automatic photo and video backup to the cloud
- App and system updates left on automatic
What things cost, roughly
Rough figures, not promises — the real number moves with the app, the video quality, and the network you land on. They are still enough to size a plan with.
| Activity | Roughly | Worth knowing |
|---|---|---|
| Maps and turn-by-turn navigation | ~5 MB an hour | Cheaper still if you download the area before you leave Wi-Fi. |
| Messaging — text, the odd photo | ~10 MB a day | Sending videos is the part that adds up, not the chatting. |
| Email, search, reading | 20–60 MB an hour | Image-heavy pages sit at the top of that range. |
| Music streaming | 50–100 MB an hour | Downloaded playlists cost nothing on the road. |
| Scrolling social feeds | ~100 MB every 10 minutes | Autoplaying video is doing almost all of that. |
| Video calls | 300–600 MB an hour | Audio-only calls are a fraction of it. |
| Video streaming | 0.7 GB an hour at standard quality, 2–3 GB at HD | One HD film can outweigh a whole week of everything else. |
| Photo and video cloud backup | A single 4K minute is ~350 MB | The classic silent drain — it runs while your phone is in your pocket. |
| Hotspot for a laptop | As much as the laptop wants | An OS update pushed over tethering can be several GB on its own. |
What a day looks like
Find the day that sounds most like yours. Most people are somewhere between the first two, and guess themselves into the third.
200–300 MB
Maps to get around, messaging, a few searches, boarding passes and tickets. No video.
500 MB – 1 GB
All of the above plus social feeds, some music, the occasional short video and a voice call home.
2 GB and up
Streaming in the evening, video calls, photos backing up as you shoot, a laptop on your hotspot.
How much for a whole trip
Multiply your day by your nights away, then round to the nearest plan on offer for your destination. If two sizes look close, take the smaller one and keep the top-up in your back pocket.
| Trip | Light | Normal | Heavy |
|---|---|---|---|
| Long weekend (3–4 days) | ~1 GB | 2–4 GB | 8 GB+ |
| One week | 1–2 GB | 3–7 GB | 15 GB+ |
| Two weeks | 3–4 GB | 7–14 GB | 30 GB+ |
| A month | 6–9 GB | 15–30 GB | Go unlimited if the destination offers it |
Travelling with someone? Only one of you needs a plan if you are happy to share it over a hotspot — just budget for two people's worth of data on that one plan.
Five habits that stretch a plan
Download before you go
Offline maps, playlists, and a couple of episodes on hotel or airport Wi-Fi cost you nothing on the road. This is the single highest-value habit.
Turn off cloud backup on cellular
Photo and video backup will happily push a day of holiday footage over your travel plan. Leave it to run when you are next on Wi-Fi.
Watch at standard quality
Dropping streaming from HD to standard cuts the bill by roughly two thirds, and on a phone screen you will barely notice.
Use Low Data Mode
On iPhone: Settings → Cellular → your SimChao line → Cellular Data Options → Low Data Mode. It quietly pauses background refresh and automatic updates.
Treat hotspot as a decision
Tethering is genuinely useful — just switch it on for the thing you need and off again afterwards, so a laptop update does not empty the plan while you are not looking.
If you run out, top up
Running dry mid-trip is a two-minute problem. You top up from the app without reinstalling anything — the eSIM stays exactly where it is and a fresh plan is added to it, so there is no QR code to find and no settings to redo.
Your remaining data and expiry date sit in the app, so you can usually see it coming. Those figures come from the local operator and can lag real usage slightly — worth a little headroom rather than cutting it to the megabyte. Very occasionally a supplier stops offering plans that fit an existing eSIM; if that happens, you buy a new eSIM instead of topping up.
Unused data does not roll over
Every plan has a validity window as well as an allowance. When the window closes, whatever you did not use expires with it — it does not carry into your next plan and it is not refundable.
It is worth checking when the clock starts, too: depending on the plan it can begin at purchase, at installation, or at first use, and the plan's description says which. That is the real argument for buying close to what you expect to use — a too-big plan does not bank the difference, it just expires with you.
One more thing: data-only means data-only
A SimChao plan carries data — no phone number, no SMS on that line. Your usual SIM keeps your number for calls and texts. Calling home over WhatsApp, FaceTime or Signal works perfectly well; it just comes out of your data, and video calls come out of it fast.