say a 100' dragon.
Lizards are weird, but just knee jerk numbers:
Komodo dragons get to be about 10' and have four inch eggs. (40" 100' dragon egg)
Saltwater crocs get to be about 20' and have 2-3" eggs (10"-15" 100' dragon egg)
Titanosaurus Blanforti got to be about 60' long and had 8"...