That varies extremely on the age, sex, and build of a person. Also, what do you mean by lift; curl, dead lift, bench?
It really all depends on the age because your muscles are not fully developed until you are eighteen years old.
in my opinion a strong six teen year old should be able to lift about 15-17Kg more than once were as a man who works out or is strong can probably lift over 20Kg
bare in mind that this is heavily using the bicep and lightly using the shoulder
NOT THE BACK MUSCLES AS WELL.
The average wight a teen can lift is probably about 5-10Kg more than once
The average wight for a man is probably about 10-18Kg