Well, Yoda seems to be 66cm talll (quick Google search), so with a good picture from head to toe and some simple math you can easily figure out all the measurements you need
Print the pic, measure it out. If he's 8cm tall on the pic, that means he is now printed 8.25 times smaller than his true size (66cm divided by 8cm). Now measure the width of his head on you print. If the head is 2.7cm wide, multiply 2.7 by the 8.25 ratio and you'll know his 1:1 head is 22.275cm wide, and so on for every measurement you need. The better the picture and the larger the print, the more precise your measurements will be.
If you look up a member named cyberman I think, he's like the Michelangelo of yoda sculpture from what I've seen
im sure his threads will help you in your venture.