eSIM Data Calculator
Tell us how long you are away and roughly how you use your phone, and we will work out how many gigabytes to buy — plus where every megabyte of it goes.
Your trip
Pick the closest starting point, then adjust anything below.
Only video and social feeds change with this — messaging and maps cost the same either way.
A typical day
Hours per day, not for the whole trip.
WhatsApp, iMessage, Telegram — text, voice notes and the odd photo.
Google or Apple Maps with directions running as you walk or drive.
News, menus, booking sites, checking mail between stops.
Instagram, TikTok, X, Reddit — feeds that autoplay video as you scroll.
Spotify, Apple Music, podcasts streamed rather than downloaded first.
FaceTime, WhatsApp video, Zoom, Google Meet — calling home.
Netflix, YouTube, Prime Video watched on the phone screen.
Laptop or tablet
A tethered laptop pulls full desktop pages and runs cloud sync, so it costs far more per hour than the phone does.
Buy at least
5GB
About 3.0 GB over 7 days, or roughly 440 MB a day.
Where it goes
Across the whole trip, largest first.The size above adds about a fifth on top of the estimate and rounds up to a size providers actually sell. Running out abroad means buying a top-up on hotel wifi; over-buying by a gigabyte costs a coffee.
What 5 GB actually buys you
If you spent the whole allowance on one thing, with quality set to Standard.
Background sync comes off the top before any of this. The greyed rows would still be running when you fly home.
Now find a plan that size
Pick where you are going and compare what 5 GB costs across the providers that cover it.
Browse destinationsHow this estimate is built
Every app you use has a rough cost per hour, and a day abroad is just those hours added together. We multiply the hours you set by a rate for each activity, add a fixed daily allowance for traffic your phone generates on its own, multiply by your trip length, then round up to a size you can actually buy.
The rates are round on purpose. Real usage varies with the app version, the network you land on and how compressed a given video happens to be, so the honest precision here is about half a band. A calculator that answers to two decimal places is claiming a measurement nobody made.
The per-hour figures we use, on a phone screen:
- Messaging — about 3 MB an hour
- Maps and navigation — about 6 MB an hour
- Web and email — about 30 MB an hour
- Social feeds — about 160 MB an hour
- Music and podcasts — about 75 MB an hour
- Video calls — about 250 MB an hour
- Video streaming — about 900 MB an hour
- Laptop on your hotspot — about 450 MB an hour, because desktop pages and cloud sync are nothing like phone traffic
- Background traffic — about 55 MB a day, whether or not you unlock the phone
Only social feeds and video streaming move with the quality switch. Data saver takes them to roughly half, high quality to nearly two and a half times, which is why two people on the same trip with the same screen time can need wildly different amounts.
Why there is headroom on top
The number we show you is the estimate plus about twenty per cent, rounded up to the next size providers sell. That is not padding for its own sake. The cost of over-buying is one size band; the cost of running out is standing in a hotel lobby trying to reach a captive portal to buy a top-up, or spending the last two days of a trip without maps. The asymmetry is enormous, so the estimate leans one way on purpose. Twenty per cent absorbs a couple of unplanned video calls home without pushing a light user up several bands for no reason.
What eats data fastest
Two things decide almost every trip: video streaming and social feeds. Everything else — messaging, maps, email, even music — is background noise next to an hour of 1080p video. If your estimate comes out higher than you expected, the fix is almost never to use your phone less.
- Turn on your phone's data saver, and the in-app one in Instagram, TikTok and YouTube. That single switch is close to halving the two activities that dominate the total.
- Download maps, playlists and anything you plan to watch over hotel or home wifi before you go. Offline maps in particular cut navigation to almost nothing.
- Turn off photo and video backup over mobile data, and stop apps refreshing in the background. That is the part of the bill you never see yourself using.
Questions people ask
How much data do I need for a week abroad?
For most travellers a week comes out somewhere between three and ten gigabytes, and the spread is almost entirely about video. A week of maps, messaging and the occasional feed scroll sits at the low end; a week with an hour of streaming a day and a laptop on your hotspot lands several times higher. Set your own days and hours above rather than trusting an average — the difference between a light and heavy week is bigger than the difference between a week and a fortnight.
Do maps use a lot of data?
No, and this surprises people. Turn-by-turn navigation is one of the cheapest things you can do with a phone — the map tiles for an area are small and get cached as you go, so an hour of directions costs a fraction of a minute of video. Downloading an offline map over wifi before you leave cuts it close to nothing. If your trip estimate is high, maps are not the reason.
Do WhatsApp calls use much data?
Voice calls over WhatsApp, Signal or FaceTime Audio are cheap — comparable to messaging, and you would struggle to notice them on a week's allowance. Video calls are a different question entirely: a video call costs roughly as much per hour as a long session of social scrolling, because it is sending a live stream as well as receiving one. Half an hour a day home to family is fine to budget for. Two hours a day is a real line on the estimate.
What happens if I run out of data?
On most travel eSIMs the data simply stops and you keep the plan until it expires. Some providers instead drop you to a throttled speed that is usable for messaging but not much else. Either way you can normally buy a top-up in the provider's app — but you need a connection to do that, which in practice means finding wifi. That is the whole reason this calculator recommends a size above its own estimate rather than exactly matching it.
Does my phone use data in the background?
Constantly. Push notifications, mail syncing, photo and video backup, app and OS updates, and the analytics calls behind almost every app all run without you opening anything. It is a floor rather than a rounding error — on a light trip it can be most of the total, and leaving it out is the commonest reason a traveller's own guess comes in under what they actually used. That is why it appears as its own line in the breakdown here instead of being folded into the activities.
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