I do 20% fat where 1 pound is fat and 4 pounds is meat making a total of 5 pounds. This means 1 out of 5 is fat (1/5) which, 1/5 = 20%
This is my go-to ration because it flat out works well for every sausage, burger, meatloaf, taco, spaghetti, etc. application I make.
Also, the math is super...