4 oz is one pack. You would use 6 to 8 oz for a weave. You may need 10 to 12 oz if the hair is longer than 16 inches. Longer hair will have a shorter weft because it's measured by weight.
guess I have a small head then bcuz I only use 4oz but I also split my tracks, I have the kinky straight hair so it's pretty thick. Didn't even use the whole pack of hair
It depends on the length and texture of the hair. General rule of thumb: if going 18" or longer, most likely you would need three packs of hair especially if it is straight hair.
The most hair I ever used was 10oz of hair plus a closure which is like 2 ounces (team big head over here)