Former curtain sales advisor here. There are two main styles of curtain when you buy ready made, pencil pleat and eyelet.
Pencil pleat are the more traditional type that look “pleated” at the top due to you gathering them in with strings attached to the back of the curtain. To give you enough material to create this gather, you need approximately double the amount of material in comparison to the size of your window. So for the space that you’ve measured at 220cm, a pair of curtains at 230cm wide (curtains measurements are given per curtain, so each curtain in this set is 230cm wide - 460cm of material] is what you need. Pencil pleat curtains can be hung on a track or a pole with rings attached to which you can hook the tape onto.
Eyelet curtains are generally thought of as a little bit more modern, and don’t require you to gather them in using strings. The eyelets {rings} are set into the curtain already and you feed the curtain onto the curtain pole to hang it. As you don’t gather them, you can get away with slightly less material, usually around 1.5 times the width of the space you measured as they still won’t sit flat on the pole due to the eyelets. So 1.5 times 220 would be 330, meaning you could get away with a set of curtains at 170 wide, giving you 340cm of material altogether. You could also use the 230 width to make the curtains look more generously sized when closed, but that’s personal preference.
Certain shops list their sizes differently to above, but go with a rule of 2x width for pencil please, 1.5 width for eyelet and you won’t go far wrong.
I can answer more questions if helpful too :)