It's difficult to grasp the concept of PARTS, but once you get the hang, it's easier than you think. 15 oz to 1 oz is 16 oz of material. 7.5 oz to .5 oz is the same thing, only half the material. 3.75 oz to .25 oz is the same thing only half of that. You don't need a scale, just a calculator. When they say "by weight", they have figured out already how many Ounces of this, is necessary for how many ounces of that.
Most automotive paints are measured in Parts. The paint cups that you purchase for measuring even have the most popular weights or parts printed on them.
Clear as mud right? Do some searches on Automotive Painting/Parts. all sorts of explanations will show up. Personally, I would like someone to make an online calculator where you put the number of ounces you want, and how many of each part is required, and it just tells you. Haven't found that yet. Good Luck!
