text: do i weigh too much?? i am 12 and i am about 5.7' and i weigh omewhere in the range of 115-120 i am almost positive. my bmi is 18.2 which for me is underweight. my thighs are big but i have a small torso and my waist is small is that to uinderwieght,normal or overweight? at 12 years old, you're probably feeling a little self-conscious about how your body is changing.  you are right that a bmi of 18.7 is underweight, but as long as you eat a healthy diet, you should be ok.  (you most certainly do not weigh too much)  your body will continue to change, so the proportions you have now will most likely not be the proportions you have next year.    be proud of your height!  you may not like being the tallest girl in your class, but as you get older, you will love how clothes look on you.  hold your head high!