i havent read what everyone else wrote this is the halacha not sure who says it:
from the knees and up you cannot even see the form that means your tight/leggigs or whatever you want to wear…abpve the knee has to be covered by a skirt and then from the knee and down its not assur to show the form therefore we are allowed to wear tights/ leggiings etc.
and the four inches below your knee IS NOT halacha its just something ppl take on bec if your skirt is four inches then your knees will definatley not show!
i hope everything is clear now!