I am 157 cm age 12 what is my healthy weight??
You shouldn't worry a about your weight a that age you will be constantly growing and your body will change everyday
Yeah bmi calculators won't calculate for that age, there is no recommended weight endorsed by doctors. However, you can easily tell if you might need to be getting a little more exercise.
If you're concerned, try eating less processed foods and stick with lean meats and real whole foods that don't come in a box with ingredients. You know, fruits and veggies and whole grains. Get some exercise regularly. Don't try and control things too much, at that age you need a lot of crucial nutrients so just eat a lot but eat healthy. With a minimum amount of effort (or a huge amount of effort if your family keeps junk foods around) you can let your young body do half the work and be just fine and healthy.
I also worry about my weight as a thirteen year old. Apparently twelve year olds should weugh in between fourty anf fifty kgs