Trying to create a rank system by using XP and levels

So I already implemented the XP system by assigning +1 xp every time the user posts, but I want to allow them to “level up” when they hit a threshold of XP. I want the threshold of it to be 100 and when they reach that it adds + 1 to the data base entry “level” under the user data type so it ties to their account. Is this doable? If so can anyone point me in the right direction? I cant really seem to figure out how to dynamically update the entry level when a threshold is met, or even find where to put the level math so it can do its functions.

The math I was thinking would just be user xp / 100 = user level. and it wouldn’t always be a whole number for instance 130 = 1.3 and that’s not a “full level” so I would also have to figure out how to display only the next iteration of a full level