How much data do I need?
Nobody can tell you your number, and every page that gives you one made it up. What is knowable is what a size actually buys, in hours, so you can work out your own. Move along the scale below.
01The calculator
What a gigabyte actually buys
Each row assumes you did only that one thing. Real trips mix them, so these are the outer edges rather than a plan. The sizes are the ones genuinely on sale, not a made-up scale.
Gigabytes
- Maps, turn by turn83 days5 MB an hour
- Messages and photos34 days12 MB an hour
- Music, streamed5 days72 MB an hour
- Social, scrolling2 days150 MB an hour
- Video calls home2 days200 MB an hour
- Video, streamed40 hours250 MB an hour
Each row assumes you did nothing else with the 10 GB. Real trips mix them, so treat these as the outer edges rather than a plan.
- Maps, turn by turnestimate
- Standard navigation, no satellite or 3D view. Those cost several times more.
- Messages and photosestimate
- Chat apps sending compressed photos. Text alone is a rounding error.
- Music, streamed
- Spotify states High quality is approximately 160 kbit/s. 160 x 3600 / 8 = 72,000 kB. Spotify, audio quality
- Social, scrollingestimate
- Feeds that autoplay video. Turning autoplay off cuts this sharply.
- Video calls homeestimate
- A standard-quality video call. A voice-only call is roughly a tenth of it.
- Video, streamed
- Netflix states its Automatic mobile setting gives about 4 hours per GB. Netflix, how to control how much data Netflix uses
02Why your instinct is wrong
Your phone bill measures the wrong thing
The obvious way to size a travel plan is to look at what your phone says you used last month. It is the wrong number, and it is wrong in the direction that leaves you offline in a taxi.
At home you are on wifi for most of your waking hours: the flat, the office, the coffee shop. The mobile figure on your bill is only what leaked past those networks. Abroad there is nothing to leak past, so the same day of the same behaviour lands entirely on the eSIM. People who buy the size matching their monthly bill are sizing a plan against a fraction of their own usage.
This cuts the other way too, and more happily. The thing most people are frightened of running out of is directions, and navigation is nearly free: one gigabyte is about 8 days of continuous turn-by-turn. Download the offline map of the city before you fly and it costs nothing at all.
03Where it actually goes
One hour of video costs 50 hours of maps
Read the table above from the top down and the shape of the answer appears on its own. The hungriest row runs at 250 MB an hour and the lightest at 5. Your total is therefore set almost entirely by how much you stream, and barely at all by how much you navigate.
The quiet one is social. Feeds autoplay video whether or not you asked them to, which is why scrolling costs several times what messaging does. Turning autoplay off is the single change with the largest effect on a trip, and it is one setting.
Every figure on this page comes from the table above, where each row carries its source and the ones we could not source from a primary page are labelled as estimates. We would rather mark our own soft numbers than print six hard-looking figures and cite none.
04Questions
How much data do I need for a week abroad?
Nobody can answer that honestly without knowing what you will do with it, and a page that gives you one number made it up. What is answerable is what a size buys: at 5 GB you have roughly 41 days of turn-by-turn navigation, or 20 hours of streamed video, or something in between. Navigation is close to free and video is not, so the honest planning rule is that your number is set almost entirely by how much you stream.
Why is my usage at home a bad guide?
Because most of it is wifi. Your phone shows a mobile-data figure for the month, and at home that figure is what leaked past your home and office networks rather than what you actually consumed. Abroad there is no wifi to leak past for most of the day, so the same behaviour lands entirely on the eSIM. That is why people who confidently buy the size matching their monthly bill run out.
Does using maps abroad burn a lot of data?
No, and this is the fear that sells the most oversized plans. Standard turn-by-turn navigation runs about 5 MB an hour, so a single gigabyte covers over a week of continuous directions. Satellite and 3D views cost several times that. Downloading the offline map of your city before you fly removes even the 5 MB.
What actually uses the data?
Video, and then everything else a long way behind. Streamed video runs about 250 MB an hour against 5 MB for navigation, so an hour of video costs the same as fifty hours of directions. Social feeds are the quiet one, because they autoplay video without being asked. Turning autoplay off cuts that sharply and is the single change with the biggest effect.
Is this calculator free?
Yes, and it needs no account, no email and no card. It is one of several free tools here, alongside a phone number checker and the full published call rate card for 220 countries. We sell travel data and calling credit; the tools are free because a person who can check something for themselves is the person who trusts the answer.
When you know your size
Travel data starts at $3.40, and the sizes on the scale above are the ones on sale. Prices differ by destination, so the store quotes yours before you pay.
The other free toolsPick a size for your trip
Choose a destination and install the plan before you fly, while you still have wifi.