How much data do you actually need abroad

Almost everybody buys more than they need. Then they come home with six unused gigabytes and buy more next time, because they remember "nearly running out" on the day they watched a film on a delayed plane.

Here is what it actually looks like, with figures you can check on your own phone.

What costs very little

These are the things that make people think they need a big plan, and which are in fact pennies:

• Messaging. WhatsApp, Viber, Signal — a thousand messages in a day is a few megabytes. Text is nearly free.
• Maps, once the area is downloaded. Navigation itself uses very little; what uses data is fetching a map you do not have.
• Search, timetables, menus. A few megabytes an hour, and that is while you are constantly looking.
• Voice calls over the internet. About a megabyte a minute. An hour of talking is 60 MB — less than one full-size photo sent twice.

What costs a great deal

Nearly everything that really eats a plan comes down to three things:

• Photo and video backup. First, second and third place. A day of shooting on a phone that uploads everything is easily 2 to 5 GB. A single minute of full-resolution video can be 150 MB on its own.
• Video calls. Around 200–400 MB an hour. Fine occasionally; every evening for a week and that is half a plan.
• Streaming. 0.7 to 3 GB an hour depending on quality. One HD film is an entire average plan.

If you change one thing before a trip, make it photo backup to WiFi only. It saves more than every other decision combined.

How much for seven days

With automatic backup off and no streaming over mobile data:

• Light — maps, messaging, a little searching, photos on WiFi only: 1 to 2 GB.
• Normal — all of the above plus social media, the odd video call, sending photos during the day: 3 to 5 GB.
• Working from the trip — email, meetings, tethering a laptop: 8 to 15 GB.
• Nothing configured at all — everything on, nothing adjusted: 15 GB and up, most of it on syncing.

For a fortnight, double it — though not quite linearly, since the first days cost more while maps cache.

Minutes and SMS: do you need them at all

Usually not, and it is worth understanding why.

If you leave your own number switched on for calls with its data roaming off, you still receive calls and SMS — including bank codes. Receiving SMS while roaming is normally free; receiving calls may carry a charge depending on your operator, but nothing consumes your data.

So a plan with minutes is only worth it if you have to ring local numbers — a taxi, a restaurant, whoever holds the keys. For everything else an internet call does the same job and spends megabytes instead of minutes.

If you do need local calls, we have plans with a number — but they are not something to buy out of habit.

Three settings before you fly

1. Backup to WiFi only. On iPhone: Settings → your name → iCloud → Photos. On Android: Google Photos → backup settings.
2. Download the area map. Google Maps, Organic Maps or Maps.me all do it, and a region fits in a few hundred megabytes over home WiFi.
3. Turn off automatic app updates over mobile data. One large update can be a gigabyte.

What if you do run out

Top up from the app while you still have a signal, or on WiFi. Do not leave it to the last hundred megabytes — topping up needs internet, and internet is precisely what you have run out of.

A working rule: buy your estimate plus a third. Cheaper than topping up in a hurry, and far cheaper than being without a map.