eSIM or roaming: what a two-week trip actually costs

Roaming is the default because it requires no decision. You land, your phone connects, and the cost shows up weeks later on a bill you've stopped associating with the trip. That delay is the whole reason the arithmetic below surprises people.

So here is the arithmetic, for one specific trip: fourteen days in Japan, one traveller, ordinary use — maps, messaging, a few searches, the occasional video. We priced it three ways.

The three options

Every traveller picks from the same three, whether or not they think about it that way.

1. Carrier roaming — do nothing, use your existing plan abroad, pay your carrier's daily or per-megabyte rate.
2. A local SIM — buy a physical SIM on arrival, usually at the airport, swap out your own.
3. A travel eSIM — buy a data plan before you leave, install it at home, and it connects when you land.

Option one: carrier roaming

Most large carriers now sell roaming as a daily pass rather than per megabyte, which is a genuine improvement — an accidental video call no longer costs hundreds. But the daily rate is charged for every day you use data, and Japan sits outside the cheap zone for most European and North American plans.

Call it $107 at the cheap end and $168 at the expensive end for two weeks of data you'd have used anyway. Some carriers cap the number of billed days per month, and some bundle a handful of destinations; the rates above are the published consumer prices for a destination outside those bundles, and they change — check yours before you travel rather than trusting a number in an article.

Option two: a local SIM at the airport

Buying locally is often the cheapest per gigabyte, and in Japan you can find tourist data SIMs from around ¥2,000–¥3,500 for a couple of weeks. On price alone this competes well.

The costs that don't appear on the receipt are the ones worth counting. You land without data, so you can't call an onward ride or check a booking until you've found the counter. The counter may have a queue, or be closed at the hour your flight arrived, or be in the terminal you didn't land at. You swap out your own SIM, which means your usual number stops receiving calls and texts — including two-factor codes from your bank, at exactly the moment you're about to spend money abroad. And you now own a small piece of plastic you must not lose for the duration of the trip.

None of that is fatal. It's just an hour of your first day, plus a running low-level risk, in exchange for saving a few dollars against the eSIM price.

Option three: an eSIM bought before you go

Here are DeSim's real prices for Japan, taken from the live catalogue as this was written:

For a fortnight, the 5 GB fifteen-day plan at $23.99 is the natural fit. Against carrier roaming that's a saving of roughly $83 at the cheap end and $144 at the expensive end — for the same fortnight, on the same phone, doing the same things.

The catch worth naming: 5 GB is a real limit. If you tether a laptop, upload video, or stream music on a long train journey, you will pass it. The 10 GB plan at $41.99 still lands well under every roaming figure above, and you can top up mid-trip if you misjudge.

The comparison, in one table

When roaming is genuinely the right answer

An honest comparison has to include the cases where the default wins, and there are three.

• Your destination is already included. Most EU carriers roam free within the EU, and several US plans include Mexico and Canada. If you're covered, roaming costs nothing extra and an eSIM is a pointless purchase.
• You're away for two days. At $12 per day, a weekend costs $24 — close enough to the eSIM that the difference isn't worth a decision.
• You need a working phone number abroad, not just data. Travel eSIMs are data-only. If someone has to be able to ring your usual number and you can't rely on wi-fi calling, roaming does something an eSIM doesn't.

What we'd actually do

For a trip of four days or more, outside your carrier's included zone: buy the eSIM before you fly. The saving is real, the setup takes about a minute, and you land connected rather than hunting for a shop with your bags still on your shoulder.

For a short hop inside a zone your plan already covers: do nothing. You're already paying for it.

And whichever you choose, check your carrier's current rate before you go. The numbers in this article were accurate when it was written, and roaming pricing changes more often than anyone reads the emails about it.