Monster high head size comparison with Barbie and Bratz.
You can also see the neck hole size and the big annoying neck anchor:
For a mid calf length reroot of Draculaura, I used 75% of 1 RD hank of Wild Lavender and less than 2 RD hanks of Sherbert Pink but she’s rooted very thickly.
I think you could probably reroot a monster high doll with 2 RD hanks.