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A free calculator from Japan Life Lab: enter your days in Japan and your daily phone habits to get the total GB you need and the eSIM plan size to buy. It uses published per-hour data figures from NTT Docomo and So-net.
Set your trip length and a typical day of phone use to estimate how many GB you need and which eSIM plan size to buy. Requires JavaScript.
Data use per hour, by activity
The calculator multiplies your hours per day by these published averages, applies the Wi-Fi offload you selected, and adds a 25% safety margin (networks re-download images, apps refresh in the background, and you will always use more on day 1).
| Activity | Data per hour | Published figure |
|---|---|---|
| YouTube 360p / 480p / 720p / 1080p | 0.3 / 0.5 / 1.1 / 2.3 GB | NTT Docomo (Ouchi Net Press, 2023) |
| Instagram feed / stories & reels | 0.86 / 0.43 GB | So-net PreBell (2024) |
| X (Twitter) timeline | 0.25 GB | So-net PreBell (2024) |
| Zoom / Google Meet, camera on | 0.6 GB | So-net PreBell (2024) |
| LINE video call / voice call | 0.3 GB / 0.02 GB | So-net PreBell (2024); Docomo: 1 GB ≈ 3.25 h video, 55 h voice |
| Spotify standard / high quality | 43 / 72 MB | So-net PreBell (2024) |
| Web browsing (text-heavy pages) | ≈16–20 MB | So-net: 40 pages/h ≈ 16 MB; Docomo: 1 GB ≈ 3,300 pages |
| Google Maps turn-by-turn navigation | ≈30–60 MB (≈5 MB if you never re-search) | Google Maps help via MyBestSIM (2026); Holafly guide |
| Google Maps with Street View / satellite | 0.1–1 GB | Holafly guide; MyBestSIM (2026) |
| Smartphone photo / 30-second 1080p clip | ≈3 MB / ≈30 MB each | Typical file sizes (HEIF/JPEG 2–4 MB; 1080p30 ≈ 60 MB per minute) |
Which eSIM size do travelers actually need?
- Light user, 7 days (maps 2 h, browsing 1 h, a little social, evenings on hotel Wi-Fi): roughly 2–3 GB. A 3 GB or 5 GB plan is plenty.
- Typical user, 7 days (the defaults above): roughly 5–8 GB. Choose 10 GB, or a 1 GB/day plan if you stream on Wi-Fi only.
- Heavy user (hours of Instagram/TikTok on trains, YouTube at 720p+, daily video calls): 15 GB+ per week. An unlimited plan usually costs less than topping up twice.
- Families or groups sharing a hotspot: multiply by the number of phones connected, then add another 25%.
FAQ
Does Google Maps work offline in Japan?
Yes. Open Google Maps → your profile → Offline maps → Select your own map, and download Tokyo, Osaka–Kyoto or wherever you are going. Driving and walking directions then work with almost no data. Transit directions (train times, platforms) still need a connection, which is why we keep a small per-hour allowance for maps.
Do Suica, PayPay or QR-code payments use much data?
Almost none — a few kilobytes per transaction. The messaging & background line in the calculator (30 MB/day) already covers wallets, weather, email and app refreshes.
Is 5G worth it for a tourist?
Speed does not change how much data you use — a 480p video is 0.5 GB per hour on 4G or 5G. What changes is that 5G tempts you into higher video quality, so keep your streaming apps on “data saver” if you buy a small plan.
What if I run out?
Most eSIM apps (Airalo, Nomad, Ubigi) let you top up in a minute. Holafly and IIJmio tourist plans either are unlimited or sell a fixed amount, so size those correctly from the start. Free Wi-Fi is common in hotels, convenience stores, Starbucks and on JR/Shinkansen trains, and it is the cheapest way to stretch a small plan.
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