>>7599625
Head sizes on anime style figures vary wildly so I like to use the simplified form that Will Weston teaches

head+neck - pit of the neck to bottom of ribcage - bottom of ribcage to bottom of pelvis 1:1:1

legs are half of the body, and knees are half of the leg
some things like scapula and clavicle you can use the length of a hand

He teaches this in that 2 hour class that people were sharing here a few years ago, maybe someone still has it in the video course thread, but his Instagram is also full of this stuff