The whole figure is supposed to be 6 inches tall, so with an oversized head like that I thought it might be close to the right size.
However this youtube video implies that it's about 50% too big (unless you want a Sideshow Joker -- I kid!) Too bad, since it looks like a pretty good sculpt.
Just as I thought. I mean it is supposed to be a bobble head so the head should be pretty big. If the figure was a 3 3/4" figure, then a 1:6 head might have worked Looks more like a PF sized head.