When choosing an eSIM for a trip to Japan, the question that trips up most travelers is simple: how many gigabytes should I actually buy? The short answer is that your data needs come down to "how you use your phone each day × how many days you stay." If you mostly rely on maps, messaging apps, and search, plan for roughly 0.5GB a day. If you add social media and some video, expect 1–1.5GB a day. And if you watch a lot of video or tether other devices, around 3GB a day is a reasonable estimate. Start with the quick-reference table below and find where your length of stay meets your usage style.
Quick-Reference Table: Data by Length of Stay
This is a rough guide that multiplies "daily usage" by "number of days." Actual consumption shifts depending on the apps you use and how long you stream, so when in doubt, choosing the next size up gives you a comfortable buffer.
| Length of stay | Light (0.5GB/day) | Standard (~1.5GB/day) | Heavy (3GB/day+) |
|---|---|---|---|
| 1 week (7 days) | ~3GB | ~10GB | ~20GB |
| 2 weeks (14 days) | ~7GB | ~20GB | Consider an unlimited plan |
| 3 weeks (21 days) | ~10GB | ~30GB | Consider an unlimited plan |
| 1 month (30 days) | ~15GB | ~45GB | Consider an unlimited plan |
If you're not sure which type you are, think about how much video you usually watch on your phone. If you often stream video or make video calls while you're out and away from Wi-Fi, you'll lean toward "standard to heavy." If you're mostly on Wi-Fi at your home base or accommodation and only use maps and messaging when you're out, you're closer to "light." You can match specific plans and pricing to your length of stay and data needs on our eSIM comparison page.
3 Factors That Drive How Much Data You'll Use
Even for the same number of days, the amount of data people need varies. Checking these three points before you buy helps you avoid over- or under-estimating.
1. How much Wi-Fi access you'll have
The more time you spend on Wi-Fi—at your accommodation, hotels, or cafés—the less data your eSIM consumes. If you're mostly on Wi-Fi, you'll often use less than the table suggests.
2. How often you stream video or make video calls
Video streaming and video calls use the most data by far. If you frequently watch video on the go or have long video calls with family, it's worth planning for one size up.
3. Whether you'll use tethering (sharing with other devices)
If you share your phone's data with a laptop or tablet, usage can climb quickly. If you plan to tether, a larger allowance—or an unlimited plan—becomes a sensible option. For a fuller picture of how to stay connected both abroad and locally, see our guide comparing connectivity options at home and abroad.
Estimated Daily Data Use by Usage Style
Having a concrete sense of "how many GB a day" makes choosing a size much easier. These are general estimates only and will vary with the network and your quality settings.
| Usage style | Typical activities | Daily estimate |
|---|---|---|
| Light | WhatsApp, maps, search, email | ~0.3–0.5GB |
| Standard | The above + social media, occasional video | ~1–1.5GB |
| Heavy | Video streaming, video calls, tethering | ~3GB+ |
For example, if you're staying a week and only use messaging and maps when you're out, around 3GB is often enough. If you're staying two weeks and do a fair amount of social media and video, budgeting around 20GB gives you peace of mind.
Bloomy Plans for Your Stay and How to Choose a Size
Bloomy offers data-only eSIMs you can use within Japan. Here are some representative sizes and validity periods (pricing and details may change, so please confirm the latest on the comparison page at the time of purchase).
| Data | Validity | Good for (guide) |
|---|---|---|
| 1GB | 7 days | Very light use over a few days, or as a backup |
| 3GB | 30 days | Short stays with mostly Wi-Fi, light use |
| 10GB | 30 days | Standard use over 1–2 weeks |
| 20GB | 30 days | Standard use over 2 weeks to a month |
| 50GB | 30 days | A full month with heavier use |
The trick is to pick the size closest to the estimate from the quick-reference table, and go one step up if you're unsure. The validity period matters too: a plan that's valid a little longer than your stay gives you breathing room around your arrival and departure days. Before you get started, it's also worth checking that your device supports eSIM on our eSIM-compatible devices page.
Things to Know About Data-Only eSIMs (Phone Numbers & SMS Verification)
Just as important as the data size is the fact that Bloomy is a data-only service. It does not include a phone number, the ability to send or receive SMS (text messages), or voice calling. Overlooking this can cause headaches during your stay, so it's worth understanding up front.
- No phone number is included. You can't make or receive calls on a local number.
- You can't receive SMS verification codes. If you need SMS one-time passwords from banks, government services, or other accounts, you'll need a separate method.
- App-based calls and messages through services like WhatsApp may work as long as you have a working data connection.
If you think you'll need SMS verification or a phone number during your stay, it's worth pairing your eSIM with a number-capable SIM or keeping a number active another way. We cover how to think about numbers and SMS in detail in our phone number & SMS guides. Thinking of it as "data via eSIM, a number via a separate method" makes the decision much clearer.
Heavy Use or a Long Stay? An Unlimited Plan Is an Option
If you'd rather not track your data closely, or you expect heavy use including tethering, an unlimited-type plan may be a good fit. Keep in mind, though, that unlimited plans typically may reduce speeds after a certain amount of usage, and often come with a fair-use policy and tethering conditions. "Unlimited" doesn't mean "no conditions whatsoever no matter how much you use"—it's worth understanding that before you buy.
You can review how the premium unlimited tier is positioned and its conditions on the Bloomy Unlimited Max page. That said, for many trips a "size that matches your usage" plan is easier on the budget and often more than enough. Whether a sized data plan or an unlimited plan suits you better comes down to your length of stay and how you use your phone.
If You Run Low on Data or Can't Connect
If you end up using more than you expected, there's no need to panic. With Bloomy, you can top up by adding data to the same eSIM. If you're worried about your remaining balance, it helps to know how to add data before you get started (you can learn more about adding data and how it works in our guide to data top-ups and auto-charge).
If you feel like you "can't connect," start by toggling airplane mode on and off, checking your mobile data and data roaming settings, and confirming your network selection. In most cases, a quick settings check resolves it. For any finer questions before or after purchase, compare plans by length of stay and data size on the comparison page as you prepare. Connection quality can vary depending on the local network, your device, and the area you're in.
