Almost nobody knows how much mobile data they use. At home you never had to — the allowance renews every month and the number is invisible. Then you buy a travel plan and are suddenly asked to guess, in gigabytes, for a week you have not had yet.
Guessing wrong is expensive in both directions. Too little and you are rationing maps on day five. Too much and you paid for data that expired unused. This article replaces the guess with arithmetic: what things actually cost per hour, what a realistic week adds up to, and the handful of settings that change the answer more than anything else you will do.
Key takeaways
- Video is the only thing that matters. Everything travellers worry about — maps, messages, bookings — is rounding error beside it.
- Most trips land in a middle band; the light and heavy ends are further apart than people expect.
- Six settings, done once before you fly, turn a heavy week into a moderate one.
- Size the plan for the days as well as the gigabytes — validity runs out too.
What Things Actually Cost, per Hour
These are the figures that matter. Two independent sources were used and they agree closely; treat them as good working numbers rather than laboratory precision, because quality settings, network speed and screen size all move them.
| Activity | Roughly, per hour |
|---|---|
| Maps navigation | 5 MB |
| Messaging, text only | Under 5 MB |
| eMail and web browsing | 30–60 MB |
| Music streaming, normal quality | 40 MB |
| Music streaming, highest quality | 145 MB |
| Voice call over a messaging app | 40 MB |
| Photo feed scrolling | 120 MB |
| Video call, one to one | 250 MB |
| Short-video scrolling, data saver on | 360 MB |
| Stories and reels | 600 MB |
| Video streaming, standard quality | 700 MB |
| Short-video scrolling, default quality | 840 MB |
| Video streaming, HD | 3 GB |
| Video streaming, 4K | 7 GB |
The Only Thing You Really Need to Notice
Navigating all day costs less than four minutes of HD video.
Look at the top of that table and then the bottom — that one comparison answers most of the question.
The things travellers worry about — maps, messages, looking up opening times, calling a taxi, checking a booking — are all in the first four rows and are collectively trivial. Everything that consumes a travel plan lives in the last six rows, and every one of them is video.
An hour of video in the evening moves a week further than every map, message and booking put together. Size the plan for this, and the rest looks after itself.
Three Weeks, Costed
Same seven-day trip, three different people. The numbers are the table above, multiplied out.
The Navigator
Maps for three hours a day, messaging throughout, a dozen searches, a few photos sent, no video. Wi-Fi at the hotel each evening.
Roughly 1 GB for the week. Realistically under it. This person consistently overbuys.
The Normal Traveller
All of the above, plus half an hour of social scrolling a day, a daily video call home, some music on the train, and the occasional video that autoplays whether they wanted it or not.
Roughly 3–5 GB for the week. This is the great majority of people and the range most trips land in.
The Always-On
Phone as primary screen. An hour or two of short-video a day, streaming instead of hotel Wi-Fi, hotspot to a laptop for a couple of work sessions, photos backing up automatically.
10 GB and upwards. Note how quickly this one moves: two hours of default-quality short video every day is 12 GB on its own.
Do the Arithmetic Yourself
Two minutes with the table beats any rule of thumb:
- Write down the hours per day for each activity you will genuinely do on mobile data — not on hotel Wi-Fi.
- Multiply each by the figure in the table.
- Add them, multiply by the number of days.
- Add 30%. Not for safety margin theatre — for the things in the next section, which you will not think of.
What Inflates the Number While You Are Not Looking
The gap between what people calculate and what they use is almost always one of these five:
- Photo and video backup. The single biggest offender by a distance. A day of holiday photos syncing to the cloud can outweigh everything else you did on the phone. Most people have this on and have forgotten.
- Autoplaying video. Social feeds play video by default. You are not choosing to watch it and it costs the same as if you were.
- App updates. Phones are usually set to update over Wi-Fi only, but "usually" is doing a lot of work in that sentence — check rather than assume.
- Background refresh. Dozens of apps quietly polling for updates all day. Individually tiny, collectively not.
- Hotspot. A laptop behaves nothing like a phone. It downloads updates, syncs cloud folders and streams at full desktop quality without asking.
Six Settings, Before You Fly
Do these once and a heavy week becomes a moderate one. All of them are on your phone already.
-
Turn photo backup to Wi-Fi only
If you change one thing, change this one.
-
Download your maps offline
Save the city or region before you leave and navigation costs almost nothing.
-
Turn off autoplay
In every social app. The setting exists in all of them and is usually two menus deep.
-
Turn on data saver
In your video and short-video apps. Roughly halves them, and on a phone screen most people cannot see the difference.
-
Download music and shows over Wi-Fi
The night before, rather than streaming them on the move.
-
Restrict background refresh
To the handful of apps that genuinely need it.
Café and hotel connections genuinely carry a lot of a trip. They are also the thing that is missing on the afternoon you most need a map, so plan the data as though they will not be there.
Wi-Fi Is Real, but Do Not Plan Around It
Hotels, cafés, airports and most accommodation have Wi-Fi, and for a traveller who is out all day and back by evening it genuinely absorbs the heavy usage — the shows, the backups, the video calls home.
What it will not do is cover you between places, which is exactly when you need maps, transport apps and the address of where you are going. Plan your data for the hours you are moving around, and treat Wi-Fi as the thing that keeps the number from growing rather than the thing you depend on.
How Long, Not Just How Much
Every plan has two numbers and travellers only ever look at one. The allowance is the gigabytes. The validity is how long you have to use them, and when it runs out the remaining data goes with it.
The clock starts on first connection, not at purchase — so buying two weeks early costs you nothing. But it is measured to the minute, not to the day: a seven-day plan that first connects at 14:55 on a Monday expires at 14:55 the following Monday, not at midnight.
Two consequences worth planning around. If you land late in the evening, a plan whose validity ends the morning you fly home may leave you without data for the trip to the airport — usually the one moment you genuinely need maps and a transport app. And a plan that is generous on data but short on days is not the bargain it looks like, because you cannot spread the allowance over a longer trip.
Match the days first, then the gigabytes. It is the cheaper of the two mistakes to correct.
If You Are Visiting More than One Country
A plan bought for one destination works in that destination. Cross a border and it stops, which is a rude surprise on a rail trip or an island hop.
Two ways around it, and the arithmetic is worth doing rather than assuming:
- A regional plan covering the whole area you are moving through. Usually the better answer for three or more countries, and always the better answer if you will be crossing borders overland where you cannot easily stop and buy something.
- Separate plans per country. Often cheaper for two countries, particularly if you are spending most of the trip in one of them and only passing through the other. There is nothing wrong with holding two travel eSIMs and switching which one carries data — modern phones store several profiles.
The one thing not to do is buy for your first stop and improvise later. Buying data while you have no data is the problem that has no good solution.
Unlimited: When It Earns Its Price
Unlimited plans are worth it for a genuinely narrow set of people — someone streaming daily instead of using Wi-Fi, someone hotspotting a laptop for real work, someone on a long trip who would rather not think about it at all.
For everyone else it is insurance against a risk that did not exist. If your honest arithmetic lands near the Normal Traveller above, an unlimited plan is a premium paid for headroom you will not reach. Two things worth knowing before you buy one: most unlimited plans slow down after a threshold rather than cutting off, and many restrict or exclude hotspot use — which is often the exact reason someone wanted unlimited in the first place. Read those two lines on the plan.
Check What You Actually Used
The best possible input for your next trip is your last one. Both platforms track it:
- iPhone: SettingsMobile Data. Scroll down for a per-app breakdown. Reset the statistics when you land so the figure covers the trip and not the last three years.
- Android: SettingsNetwork & InternetData usage, or SIM settings on some manufacturers. You can set a warning and a hard limit here, which is worth doing.
Do this once and you will never guess again — you will know your own number, which is worth more than any table.
Common Questions
Does the Unused Data Roll Over?
No. When the validity ends, whatever is left ends with it. This is why matching the days matters as much as matching the gigabytes.
Can I Top Up Mid-Trip?
Yes, and it takes about a minute — which is the reason buying slightly under is the safer error. You do need some connection to do it, so a café or hotel Wi-Fi is the moment to handle it rather than waiting until you are on a train.
Does a Hotspot Use More Data than Using the Phone?
The sharing itself costs nothing extra, but what you share it with matters enormously. A laptop syncs cloud folders, downloads updates and streams at desktop quality — it can quietly outspend the phone several times over in an afternoon.
Do Calls and Texts Come out of My Data?
Calls and messages made through apps do, and they are cheap — a voice call is about the same as a few minutes of scrolling. Ordinary calls and SMS on your home number run on your home line and its own tariff, not on the travel plan.
How Do I Know When I Am Running Low?
Your account shows the remaining allowance, and both phone platforms let you set a data warning at a number you choose. Setting one on the day you land is thirty seconds well spent.
If You Are Still Not Sure
Buy for the middle and top up if you need to. A travel eSIM is not a one-shot purchase: running out is an inconvenience of about ninety seconds, whereas over-buying is money that expires. Starting a size down is the cheaper mistake, and it is the one you can fix from the arrivals hall.
When you know roughly what you need, compare the plans for your destination — several mobile networks usually cover the same place and they price allowances very differently. If you have not bought one before, start with what an eSIM is and how it works, then how to install it.
See what a plan for your destination costs Sizes and validity side by side, so the arithmetic above meets a real price.
