What is the average size of a 3 year old boy?

There is no "normal" height! My son has always been tall and thin, but weighs alot due to muscle mass. He is about 3'6.5 as of this morning...thats 42.5 inches and he turns 3 next month. He weighed in at 43lbs also! As long as your child is gaining weight and height proportionally everything is fine!