You can not calculate a healthy weight by age and average as everybody is genetically differant.
The best way to check the health of the twelve year old is.
BMI, (body mass index), which is calculated by either:-
Height and weight.
OR
Weight and waist size.
Around 70 to 80 pounds or so.
Well it mainly depends on your body shape but most average 12 year olds are 7 to 9 stone.
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the average height is 5"3
even if u ask for a doctors opinion there is NO "average" for an 11 12 or 13 teen yr old. there is an average for u depending on ur geans of ur parents and height but not for a whole selection of girls.
The average 13 year old's weight is about 105-135 lbs.
110-150
the average is about 5'6 to 5'7 and 140.
40-50 lbs.
You cannot express weight in centimeters.
about 80-100 pounds.
Around 70 to 80 pounds or so.
The average is 45kg, but in the 50's is ok.
About 150 pounds
it is 35 or 36
85 pounds
i am an athlete and a 11 year old girl i weigh 74lbs