Children who are 8-years-old should weigh about 57 pounds, according to Disabled World. Boys at 8 years weigh an average of one-half pound less because they are slightly shorter. Eight-year-old children are typically about 50.5 inches tall.
Children in the 95th percentile of weight for their age group are at risk of becoming overweight, according to pediatrics expert Dr. Vincent Iannelli for About.com. Parents who are concerned about a child's weight should consult with medical professionals. Doctors advise cutting down on junk food and increasing activity so children do not become overweight. Some girls around age 8 put on extra weight as they approach the age of puberty.