Data allowances are where networks make the most money from over-selling. Plans jump from 5GB to 30GB to 100GB to unlimited, and the fear of running out nudges people up a tier or two they never touch. The fix is to know your number.
Find out what you use now
Your phone already tracks this. On an iPhone it is under Settings → Mobile Data; on Android, Settings → Network & internet → SIMs → App data usage (the exact path varies by manufacturer). Your network's app will also show usage per billing month. Look at the last three months and take the highest — that is your baseline.
Rough costs of common things
These are approximations; apps change their compression all the time. But they are the right order of magnitude.
| Activity | Roughly |
|---|---|
| Messaging, email, browsing | A few hundred MB a month for most people |
| Music streaming | 50–150MB per hour |
| Maps and navigation | Small — tens of MB per hour, less with offline maps |
| Social media with autoplaying video | Can be 1GB or more per hour of scrolling |
| Video calls | Roughly 0.5–1GB per hour |
| HD video streaming | 1–3GB per hour |
| Tethering a laptop | Whatever the laptop does — often the biggest surprise on a bill |
What that means in practice
- On Wi-Fi at home and work, light use out and about: 5–10GB is plenty, and many people use under 3GB.
- Commuting with music and podcasts, some social media: 15–30GB.
- Regular video on the move, or you tether a laptop: 50–100GB, or unlimited if the price gap is small.
- Your phone is your home broadband: unlimited, and check the fair-use policy.
Two habits that cut usage a lot
Turn off autoplay for video in the apps you use most — social apps in particular default to streaming video you did not ask for. And download playlists, podcasts and offline maps while on Wi-Fi; a 20-minute setup can halve what you pull over mobile data.
Pick the plan, not the fear
Once you have your number, give yourself some headroom — 50% more than your highest month is sensible — and stop there. On the SIM-only page you can filter by a minimum allowance so you only see plans that clear your number, and sort by price from there. Rolling 30-day plans mean that if you got it wrong, you fix it next month rather than in two years.