It depends heavily on the game. I could go do an analysis on every image and what it's hitbox is, but that would take far, far too long.In SA, Reimu's hitbox image is 10x10. The actual hitbox is somewhere from 4x4 to 6x6. Obviously not 5x5 because that would create an imbalance. It's hard to tell because bullet hitboxes vary as well. The only bullets whose hitboxes are the size of their image are the pellets, but those are too small and travel in various directions to measure properly.