Fitbounds and markercluster zoom issue

[closca]

Hello, I am having problems with fitBounds() and markercluster click. Basically, my map container width is dynamic to screen size (I am using flex). I saw that the map is constructed based on 256x256 tiles and the map size is tied to that. If my container has 550px width the map is actually 256x3 = 768. this results that the map has a hidden area of 218 px. So, when I use fitBounds, is doing it related to the map size and not the container size.

How can I make the map to be responsive?

Thank you.