Japan Prepaid SIM Data: Comparing Limited vs. Unlimited Plans

Choosing the right prepaid SIM is essential if you’re heading to Japan and plan to use your smartphone while traveling. A reliable data connection ensures you can navigate Japan’s busy cities, access translation apps, stay in touch, and share your experiences online. But with so many options available, how do you decide between a limited or unlimited data plan?

Let’s break down the pros and cons of each plan to help you figure out which one best suits your needs during your time in Japan.

Updated October 11, 2024

Key Factors When Choosing a Japan Prepaid SIM

When choosing a prepaid SIM for your trip to Japan, here are four key factors you should consider:

Data Amount	SIM plans range from a small amount of data (like 1 GB) to unlimited high-speed data with no daily limits.
Cost	Prices vary, but it's important to avoid going too cheap. In Japan, a reliable connection can make or break your trip, and lower-cost plans often come with restrictions.
Pickup and Drop-off Options	Some providers offer free shipping to your location in Japan, while others allow you to pick up your SIM card at the airport.
Customer Support	For non-Japanese speakers, English customer support is key. The most reliable providers offer quick, friendly assistance in English.

How much data do I need?

The most important factor in choosing the right SIM plan is how much data you’ll need. Running out of data mid-trip can be a hassle, especially if you rely on your phone for maps, translation, or staying connected.

Here are a few simple ways to estimate it:

Check your phone plan’s online account
Most phone providers show your past data usage, so you can see how much you use in a typical month.
Download a data monitoring app
These apps track how much data you’re using in real-time.
Search for a “Mobile Data Calculator”
A quick Google search will help you find tools to estimate your data usage based on your activity (e.g., streaming, browsing, using maps).

Once you have an idea of your data needs, you can decide between a fixed data plan or an unlimited data plan.

Comparing Limited vs. Unlimited Data Plans

Considerations	Prepaid Fixed Data	Prepaid Unlimited Data
Considerations	Prepaid Fixed Data	Daily Limit	No Daily Limit
Data Speed	4G LTE	4G LTE Much slower after daily limit	4G LTE Possibly slower after fair usage policy
Data Risk	Data can run out	Data can slow down	Data can slow down
Daily Usage Limit	No	Yes	No
Top up Required	Yes	No	No
Pricing	Cheap	Cheap to Moderate	Moderate

If you’re a budget traveler, then price is probably the most important factor. However, if you use your phone every day, a reliable data connection at a slightly higher cost is better.

How Much Data Do You Need during Your Trip to Japan?

What to Know About Limited Data Plans

What is a Limited Data Plan?

A limited data plan gives you a set amount of data (like 1 GB, 3GB, or 5 GB) for your trip. Once you use up that data, you’ll need to purchase more—this is called “topping up.” This option can save you money if you’re careful about your usage.

Pros	Cons
You never have to worry about your data speed slowing down due to reaching a daily limit.	It’s easy to overestimate your data use and buy too much for your trip, especially since you can’t get a refund for what you didn’t use.
If you are good at “budgeting” your data by limiting the amount of time you’re using apps, streaming, and making video calls, it can be a cheap option.	If you underestimate how much data you need and end up buying more, the cost per gigabyte is usually much higher than what you originally paid.

What to Know About Unlimited Data Plans

What is an Unlimited Data Plan?

Unlimited data plans are becoming more common among SIM providers, and they offer a lot of convenience, especially for heavy data users. However, there are two types of unlimited plans to consider: plans with daily limits and without daily limits.

	Pros	Cons
Daily Limit	- Your data limit is refreshed each day	- Data speed drops to 200kbps after you reach your daily limit - You still need to “budget” your data - You can’t buy additional fast data once you reach your daily limit
No Daily Limit	- Data speed for essential travel apps and tools never slows down	- The cost may be too much if you’re a budget traveler

Unlimited Plans with Daily Limits:

Some unlimited plans give you a certain amount of high-speed data each day, usually around 200 MB. Once you reach the daily limit, your connection speed will slow down, typically to around 200 kbps. This is fine for basic tasks like messaging, but it’s too slow for activities like streaming or browsing.

Unlimited Plans without Daily Limits:

On the other hand, an unlimited plan with no daily limit does include a fair usage policy. If you stream a lot of videos and music or download large files (gigabytes or greater) in a short amount of time, the policy will kick in and your data speed will slow down. However, Google Maps, translation software, social media apps, web searches, etc. (which are commonly used when traveling) are generally not affected by this policy.

What is a Fair Usage Policy?

A fair usage policy is when the network provider slows down your data speed during peak times or after using a lot of data quickly. This means that even though you technically have data, you will need to be patient while using it until the policy is turned off.

Comparing Daily Limit vs. No Daily Limit Plans

Feature	Unlimited Plan with Daily Limit	Unlimited Plan with No Daily Limit
Daily Limit	Yes, typically 200 MB per day	No
Speed After Limit	Slows to 200 kbps after limit	No slowdown unless Fair Usage Policy kicks in
Fair Usage Policy (FUP)	None	Yes, after heavy data usage
Best For	Light to moderate users	Heavy users, frequent travelers
Cost	Lower	Higher, but better for heavy data use

Other Considerations for Prepaid SIM Data in Japan

eSIMs: A Convenient Option for Newer Phones

Many newer smartphones, like iPhone 11 to 15, Google Pixel 6 to 8, and Samsung Galaxy S21 to S23, are eSIM-compatible. An eSIM is a digital SIM card that you can install by scanning a QR code, which saves you the hassle of physically swapping SIM cards. If your phone supports eSIM, it’s worth considering, as it’s quick and easy to activate.

[Learn more about eSIM options here!]

Estimating Your Data Needs in Japan

Keep in mind that you’ll likely use more data while traveling in Japan than you do at home. Why? Japan has complex transportation systems, limited free WiFi, and sometimes unclear English translations, so you may need to rely on your phone more than usual.

Here are some common activities and their typical data usage:

Google Maps for navigation: ~100 MB per hour
Streaming music: ~100–150 MB per hour
Social media browsing: ~200 MB per hour
Streaming videos: ~1-3 GB per hour (Netflix Standard Definition)

To ensure you stay connected without interruptions, consider budgeting a little extra for an unlimited plan with no daily limit. It will give you a high-speed connection without worrying about running out of data.