Converting currency with no internet

The five things to do before you fly, so the moment you land with no data is uneventful.

Landing without a working connection is normal. The eSIM does not activate, airport wifi wants an SMS you cannot receive, roaming is off because you turned it off deliberately. None of that is a problem if you spent ten minutes before the flight.

1. Make sure something on your phone converts offline

On iOS 18 and later this is already true — the Calculator app converts around 105 currencies with cached rates and no connection. Open it once before you fly so the rates are fresh. How to switch it on.

If you use a dedicated converter, open it on wifi before leaving so it has current rates stored.

2. Test it properly, in airplane mode

Airplane mode, force-quit the app, reopen, convert. This is the only test that tells you the truth, and it takes ten seconds. Plenty of apps that claim offline support fail it.

3. Learn the one-line rule for where you are going

Phones die, get stolen, and get left in taxis. A memorised rule does not. Find your currency in the cheat sheets, read the one sentence at the top, and you are covered for the whole trip.

4. Know what the mid-market rate is — and that you will not get it

Whatever number your app shows is almost certainly the mid-market rate: the midpoint of the wholesale market. It is the right number for judging whether a price is fair. It is not what you personally receive.

Expect a card to be close to it, an ATM to add a fee, and an airport bureau de change to be considerably worse. Budget the gap rather than being surprised by it.

5. Decide the card-terminal question now

At some point a card machine or an ATM will offer to charge you in your home currency instead of the local one. This is dynamic currency conversion, and the exchange rate is set by the terminal operator rather than your bank. It is almost always worse — sometimes several percent worse.

Always choose the local currency. Decide it now, so you are not deciding it with a queue behind you. This one habit will save you more money than any converter app.

The checklist

1. Open your converter on wifi so rates are current.
2. Test it in airplane mode after force-quitting.
3. Memorise the one-line rule for the local currency.
4. Remember the rate you see is not the rate you get.
5. Always pay in the local currency, never your own.