Because those prices belong to each operator, can change without announcement, and vary with the monthly package a customer already holds — two customers of the same operator can see different roaming prices on the same day. Serving a stale number would have you deciding on wrong information, which is worse than spending one minute in their app.

Enter the days that will be charged, which is usually the calendar days you are abroad including both travel days, not the number of nights. Most billing systems cut on calendar days rather than rolling 24-hour periods from first use, and a flight landing after midnight commonly adds a day people did not plan for.

The big cost is data, so switch roaming data off on the home SIM and give the data role to the eSIM line. The home SIM will still take calls and SMS, which may carry charges under your operator's own terms — a question for them, since we cannot state their rules for them. Also switch off automatic data switching if your handset offers it.

If the gap is small next to the whole trip budget, decide on other grounds: whether you need SMS codes, whether you have time to install a profile in advance, and whether knowing your ceiling before departure matters to you. A small difference should not drag you toward whichever option is more awkward for your situation.

The phone may use data over the home line at times, particularly with automatic data switching enabled, and you end up paying for the eSIM plan and roaming at once — the worst of all outcomes. Prevent it by explicitly switching roaming data off on the home SIM before you board, then checking again after you land.

No. It is the product of multiplying and subtracting what you typed. If your entered price is off, or the operator counts days differently from you, the outcome will differ from the bill. The tool is not connected to anyone's billing system — use it as a comparison aid, not a quotation.