Let’s take another look at that visualization:

So, knowing that “apparate” is a close second with 42 uses across all seven books, do you have a guess what number one could be?
It’s “expecto patronum”! That’s right. Used 44 times in the series. Well, sort of.
There are several times in the story where Harry utters the first half of the spell, but not the second. For instance, when he is learning it. And when he is overwhelmed by evil and can’t quite get out the whole spell.
Still, for the purposes of our exploration, I counted Harry’s attempts as well.
And just for fun, here’s a Top 10 list of spells across the book series. Your welcome. 🙂 -TLL
- expecto patronum (44)
- apparate (42)
- accio (34)
- disapparate (29)
- expelliarmus (27)
- stupefy (27)
- avada kedavra (21)
- riddikulus (18)
- protego (13)
- aguamenti (11)