Japan Prepaid SIM Data: Fixed vs. Unlimited Plans

If you’re reading this, you most likely have a smartphone and are planning a trip to Japan — that means you need data. Tourist SIM Cards are a great way to stay connected after you land in Japan, but with so many options, it really can be difficult to compare. If you’re shopping around for a plan, it’s important to understand what to compare before making your decision.

Updated March 19, 2024

How to Compare SIM Cards

There are four basic points to consider when comparing SIM Card plans.

Data Amount Plans range from 1 gigabyte (GB) of data to high-speed unlimited data with no daily limits.
CostThe price range is wide, but be careful with going too cheap.
Pickup and Drop-offSome providers offer free shipping to anywhere in Japan while others also have airport stores.
Reliability of SupportThe most reliable providers provide English customer support.

The most important of these considerations is data amount because you don’t want to run out of data if you are relying on it while visiting Japan. If you have time before your trip, we suggest finding out how much data you think you will need. If you’re not sure, there are a few ways to find out.

  • Check your phone plan’s online account for past monthly usage
  • Download a data monitoring app
  • Search Google for “Mobile Data Calculator”

Once you have an estimate, you can decide if you want to buy a fixed amount of data or go with an unlimited data plan (with or without daily limits). The unlimited plan guarantees that you will stay connected but at a higher price than paying for a specific amount of data.

ConsiderationsPrepaid Fixed DataPrepaid Unlimited Data
Daily LimitNo Daily Limit
Data Speed4G LTE4G LTE
Much slower after daily limit
Possibly slower after fair usage policy
Data RiskData can run outData can slow downData can slow down
Daily Usage LimitNoYesNo
Top up RequiredYesNoNo
PricingCheapCheap to ModerateModerate

If you’re a budget traveler, then price is probably the most important factor, however, if you use your phone every day, you will be much better off with having a reliable data connection at a slightly higher cost.

What to Know About Fixed Data Plans

A fixed data SIM Card plan lets you buy data by the gigabyte (like 1GB, 3GB, 5GB, etc.). Once you have used up the data, you need to buy more which is called “topping up.”

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

Unlimited data plans are becoming more common as SIM Card providers switch over from fixed data plans. It makes sense. Unlimited plans are often more reliable and less troublesome to use, however, there is one important consideration before buying: should you get a plan with or without a daily limit?

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

Going with an unlimited plan with a daily limit means that you may still be stuck in Japan without the ability to use your SIM Card rental when you need it. Most of these plans offer around 200MB of data per day. After reaching the daily limit, it is common to experience a drop in speed to about 200kbps. Also, because a daily limit is built into these plans, they usually don’t include a fair usage policy.

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.

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. What this means is that while you technically have data, you will need to be very patient while using it until the policy is turned off.

It’s important to understand the benefits and limitations of any SIM Card plan that you’re considering. If you want to stay connected without having your data come to a stop or slow down to a crawl, an unlimited plan without a daily limit is typically going to be your best option.

If you need to use large amounts of data without worrying about reaching a daily limit or activating a fair usage policy, we suggest asking the SIM Card provider if they have any special plans that fit your specific needs before placing your order.

Other Considerations when Renting Prepaid SIM Data in Japan


One thing you should keep in mind is that some phones are only eSIM compatible. eSIMs are embedded SIMs that you can install by scanning the given QR code, which saves you the hassle of changing the chips in your phone. iPhone 11 to 15, Google Pixel 6 to 8, and Samsung Galaxy S21 to S23 are some of the eSIM-compatible phone models. While some phones can install both a physical SIM and an eSIM, some latest phone models can only accept the eSIM, so be sure to check beforehand!

If you are interested in short-term eSIM plans, you can check here for more information on eSIM cards!

Another thing you should note is that what you plan to do on your trip to Japan has a big effect on how much data you will need. A good rule of thumb is to expect that you will be on your phone more in Japan than you are at home. The reason for this is that while you will be taking time to enjoy the sites and culture, you will also be dealing with complex transportation systems, limited WiFi hotspots, and poorly translated English information.

Unlimited data SIM Cards have become very affordable over the past couple of years, so we suggest budgeting just a little bit more travel money to get an unlimited plan with no daily limit, which offers a high-speed connection and no downtime!