On iPhone: Settings → Cellular
No need to install an app to track your data abroad: your iPhone already counts everything. Your Japan eSIM's usage appears under Cellular, kept separate from your usual line.
Usage for the current period appears below your list of lines, app by app — you can see exactly what's using what.
Look at the usage for your PlanJapan eSIM, not your home SIM still running alongside it in dual SIM.
Reset the statistics when you set offRight at the bottom of the screen: Reset Statistics. The iPhone never does it on its own.
On Android: Settings → Network & internet
Android makes it even simpler: it tracks each SIM separately and by period.
The wording varies by brand: on Samsung it's Connections → Data usage.
You'll see usage for that line only, broken down app by app.
Set it to 8 GB on a 10 GB eSIM, for instance: your phone warns you before you run out, with nothing to think about.
4 tips to save data without going without
Tracking your usage is good. Making it last is better. These four habits cut your data use noticeably — without changing a thing about your trip.
Download the maps for Tokyo, Kyoto or Osaka over Wi-Fi before you leave: navigation then uses very little data.
Playlists, podcasts and episodes download in the evening — and play offline on the Shinkansen.
App Store, Play Store and photo backup on Wi-Fi only: these are the biggest invisible data eaters.
Leave YouTube and social apps on automatic quality: on a phone screen you can barely tell the difference.
One last thing to keep an eye on: tethering. Everything the device connected to your hotspot uses comes out of your data allowance. Good news: tethering is included with no limit on every one of our plans.
What if you never had to count again?
With the unlimited eSIM (10 to 30 days, from €29.99), the question disappears: genuinely unlimited, no throttling — Google Maps, stories and video calls without ever checking the counter. It's the most comfortable choice for trips heavy on photos and video.
With a 10, 20 or 50 GB data eSIM (from €13.99), the rules of thumb are simple: 10 GB ≈ 7 days, 20 GB ≈ 14 days, 50 GB ≈ 14 days and beyond. And if you burn through your allowance faster than expected, top-ups are available on the site in a few clicks, with no eSIM to reinstall.
Not sure how much data you need?Answer a few questions about how you use your phone and our calculator tells you how many GB to plan for. Take the test →
