I am travelling to Spain.
If I bring a flat iron, it says rating: AC 100 volts to 127volts; power is 45 watts.
I keep hearing I need a converter. Do really? and if so......
I have an old Doace that says converter socker(26-2200w)
220-240AC to 100-120AC, 50Hertz,2200max.
Leave it at home. Converters are unreliable, especially old ones. Plugging a 110 volt into a 220/240 socket will fry your device and could damage the hotel's wiring . If you must have a flat iron, either buy a dual voltage travel appliance or buy one in Europe when you arrive.
The power coming from the socket in Spain will be 220-240 volt, going into your 100 volt iron.
You will get something between "Phhtt' and a couple of fire trucks. Flat hair not likely.
If your converter is something like this--
https://www.amazon.com/DOACE-X11-Voltage-Converter-Straightener/dp/B07M8KT525?th=1
it should , in theory, work.
I think many would suggest the ideal solution is to buy what you need in Spain; saves lugging the converter around and eliminates the opportunity for the 'oh &*^%" moment
Leave it home - converters aren't reliable. It will either mess up the hotel outlet, or it will blow up your appliance.
If you must have a flat iron, Google best DUAL VOLTAGE FLAT IRONS and be sure to flip the switch to the correct voltage.
I have a little Lovani flat iron that is dual voltage. Unlike my hair dryer, there's not even a switch to change. It's in my suitcase ready to go to Europe this week.
If you need one, buy one in Spain or get a dual voltage iron.