Which episodes in Boruto are fillers? I heard that over 45% is filler. And that is a lot. So that is why I am asking.
You might want to check this website. That list is updated regularly and you will notice that it also contains episodes which have yet to be aired. This is especially useful if you're following the series but only want to watch the canon episodes.
45% of filler episodes is a bit exaggerated. It's actually about 20%, although some canon episodes of Boruto do seem like fillers.
Most of them: if it's not manga canon then it's filler. I think there are less then 20 cannon episodes.