UHD Blu Ray movies are usually 66GB and sometimes 100GB so far.
A normal Blu Ray movie would be 25 or 50 GB, while a 1080p iTunes movie could be 3.5 or 5 GB.
A DVD would be 4.7 or 9 GB, while an iTunes SD movie is 1 or 2 GB.
Newer formats in a family get more efficient compression.