How much should a 15 year old boy weigh?

The AVERAGE is 5'5" and 123 pounds. You can look up height and weight charts to see what the recommended weight is for your height. However, keep in mind that people grow at different rates and there may be a mismatch of weight to height for a period of time. If you are too heavy, like everyone else you should increase your level of activity and reduce intake of non-nutritious foods.