Unlimited or fixed data eSIM: which should you buy?

Take a 10-day trip to Japan where you use maps, messaging and a few photo uploads. Holafly's 15-day unlimited plan is $50.50. Ubigi's 5 GB pack for 15 days is $10. Both are list prices in dollars, checked November 2, 2026. If 5 GB covers you, the fixed pack is the cheaper of the two.

The question is whether 5 GB covers you. Check first.

What a gigabyte a day looks like

I have no usage test to offer, so here is a vendor's own sorting. aloSIM's Thailand page puts travellers into tiers: Explorer at 1 to 2 GB a day for regular use and streaming, Pro at 2 to 5 GB a day for remote work, video calls and hotspotting. That is a seller's guide, and I have no measurement to set against it. It is still a more useful starting point than "how much do I use?".

By that guide, a light trip fits a fixed pack. A trip with work calls and tethering doesn't.

What unlimited limits

None of the unlimited plans I read promises full speed all day.

• Airalo's Japan page: full speed for the first 3 GB each day, then 1 Mbps. Airalo calls 1 Mbps enough for messages and maps, not heavy streaming. Seven days is 21 GB at full speed, at most.
• Nomad's US plan data: 2 GB a day at 4G/5G, then 1 Mbps.
• Holafly's Japan page: in rare cases an operator Fair Usage Policy can slow speed for up to one day. It states no daily figure. Its hotspot allowance is 1 GB per day.
• aloSIM's Thailand page: 3 GB of high-speed data a day, then 1 Mbps until the next day.

On the plans with a stated number, unlimited works like a fixed pack that refills every day. That is still better than a fixed pack for a heavy user, because the allowance resets. Holafly states no number, so I can't say how it compares.

What happens when fixed data runs out

Ubigi's page says that once a one-off plan's data is used you can top up instantly. Airalo's says that in many cases you can top up an eSIM instead of buying a new one. Holafly says an unlimited plan has no top-ups, and that when your days run out the eSIM stops working. Fixed plans fail by running out of gigabytes. Unlimited plans fail by running out of days.

Rules of thumb

• Light use for a week or less: buy fixed. The arithmetic is in the calculator.
• Daily video calls, tethering, or a rental car with navigation all day: buy unlimited, and read the cap first. The unlimited roundup ranks five by their small print.
• Unsure: buy a pack with top-up.

For the comparison against home-carrier passes, see eSIM vs roaming cost. For a plan you can read in detail, the Holafly review is the next stop, and Ubigi's plan page covers the fixed side.