How we rank · 5 min read
The price per GB trap: why the cheapest plan is one nobody should buy
We rank every plan by its real price per gigabyte. It is the only measure that lets you compare a 3 GB plan from one seller against a 10 GB plan from another and know which is the better deal. We stand by it. But it has a failure mode, and last week the failure mode was sitting at the top of 113 of our 215 country pages, telling people that the cheapest eSIM for Thailand cost two cents a gigabyte.
It did. It also cost $10 for 500 GB across five days, which is a plan for a reseller or a bus full of phones, not a person on holiday. This is the story of how per gigabyte pricing goes wrong at the extremes, what we changed, and how to read the number so it does not go wrong for you.
The arithmetic that is true and useless
A plan's price per GB is the price divided by the data. $10 for 500 GB is $0.02. The maths is correct. The problem is that price per GB assumes you will use the gigabytes. If you will not, the number you should care about is price per gigabyte used, and that is a different calculation.
| Plan | Price | Per GB on paper | Per GB if you use 3 GB |
|---|---|---|---|
| 500 GB, 5 days | $10.00 | $0.02 | $3.33 |
| 50 GB, 10 days | $11.19 | $0.22 | $3.73 |
| 5 GB, 7 days | $4.50 | $0.90 | $1.50 |
| 3 GB, 7 days | $3.60 | $1.20 | $1.20 |
Those are real Thailand plans from our tables. On paper, the 500 GB plan is 60 times cheaper than the 3 GB plan. For a traveller who uses 3 GB, it is nearly three times more expensive. The headline number and the real number point in opposite directions.
How it took over the site
The catalogue held 68,419 live plans when we found this. Only 355 of them were above 50 GB, half of one percent. But because per GB pricing falls as plans grow, those 355 had the lowest per GB figures in the catalogue, and our headline picked the lowest per GB figure. Result: 113 country pages led with a bulk pool. Thailand at $0.02. Spain and most of Europe at $0.08, from a 750 GB plan. Japan's Watchdog Pick was a 100 GB pool. The tables below the headline were fine, because they showed every plan. The headline was technically true and practically wrong.
We found it during a content audit, and it embarrassed us, because the whole point of this site is that the ranking is a calculation you can trust. A calculation that recommends a 500 GB plan to a weekend visitor is not one you can trust.
What we changed
One rule, applied everywhere a cheapest figure appears. Plans above 50 GB are still listed and still priced exactly as before. They rank after plans sized for a trip, and they cannot win the cheapest headline or the Watchdog Pick. The threshold is the same 50 GB line our regional comparisons already used, for the same reason.
The effect on the numbers was immediate and, we think, correct.
| Country | Cheapest before | Cheapest now | What the new cheapest is |
|---|---|---|---|
| Thailand | $0.02 | $0.22 | 50 GB, 10 days |
| Spain | $0.08 | $0.40 | a plan sized for a fortnight |
| Japan | $0.41 | $0.44 | 50 GB, 30 days, instead of a 100 GB pool |
| Europe (regional) | $0.08 | $0.58 | a real multi country plan |
The cheapest figures went up. That is the honest direction. Nobody was going to get Thailand data for two cents, and a comparison site that says otherwise is doing the marketing for a plan its readers should not buy.
Why not just delete the pools?
Because for some people they are the right plan. A family sharing one hotspot for a month, a remote worker with a laptop, a small tour group with one line. They will use a real fraction of 100 GB and the per GB price is genuine for them. Hiding the plans would be as dishonest as headlining them. So they stay in every table with their true price, ranked where a plan that size belongs.
How the rule shows up on the page
Three places. The headline at the top of each country page now names a plan sized for a trip. The Watchdog Pick, which is chosen by the lowest price per gigabyte in the current view, skips anything above 50 GB. And the table note under every comparison says so in plain words, so a reader who wonders why a two cent plan sits at row forty can see the reason without asking. The pools themselves are unchanged: same price, same data, same seller link. Only their position and their eligibility for the headline moved.
How to read price per GB yourself
- Decide how much data you will actually use. Our guide to how much data a week needs gives real figures. Most people land between 2 and 5 GB.
- Filter the table to that size, plus one step above it if the seller has no top ups.
- Now compare per GB. Within a size band, the lowest per GB is genuinely the best deal.
- Ignore per GB on any plan more than twice the size you need. Look at the total price instead, and ask whether the extra data is worth the extra money to you. Usually it is not.
Rule of thumb: price per GB compares plans of similar size. Total price compares plans of different sizes. Use the first to pick a seller and the second to pick a size.
What this says about comparison sites
Any site that ranks by price per GB and does not handle the extremes will show you the same distortion we showed you. The number is seductive because it is precise. Two cents is a fact. It is just a fact that answers a question you did not ask. We publish the rule and the threshold so you can hold us to it, and we would rather correct ourselves in public than let a calculation quietly recommend the wrong thing. Every country page now follows it, and the explanation sits in the table notes where the old claim used to be.
Questions people ask
What is a bulk data pool?
A plan with a very large allowance, typically 100 GB to 500 GB, sold for a short validity. They exist for resellers and for people sharing one line across many devices. The per gigabyte price is tiny because the total is enormous, but a single traveller will never use a fraction of it.
Why does price per GB mislead on huge plans?
Because you pay for the whole allowance, not the part you use. A 500 GB plan at $10 is two cents a gigabyte on paper. Use 3 GB of it and you actually paid over three dollars per gigabyte used, which is worse than a plain 3 GB plan. Per GB only means something when you will use most of the plan.
What did eSIM Watchdog change?
Plans above 50 GB are still listed and still priced honestly, but they no longer win the cheapest headline or the Watchdog Pick on any page. They rank after plans sized for a trip. The threshold is the same one our regional comparisons already used.
Why 50 GB?
It is where the catalogue changes character. Below it, plans are sized for individual travellers. Above it, nearly everything is a pool aimed at heavy sharing or resale. Only 355 of the 68,419 plans in the catalogue at the time sat above the line, but they were distorting the headline on more than half of our country pages.
Is a big plan ever the right buy?
Yes, for a laptop worker on a long trip, a family sharing one hotspot, or anyone who will genuinely use most of it. Those plans are still in every table, they just do not get called the cheapest for a traveller who will use 5 GB.
How should I read price per GB?
Alongside the plan size and the total price. Find the size you will actually use, then compare per GB within that size. A low per GB figure on a plan ten times bigger than you need is not a saving, it is a bigger bill.
Compare plans for the places in this guide
236,811 plans from 61 sellers, ranked by real price per GB, with prices checked against the shops themselves.
