How much should a average one year old way?

You mean weigh? There is no correct answer to this, It also depends on birth weight and in general a baby should triple his/her birthweight at 1 yr of age. Boys generally weigh a little more. Generally weight at 1 yr between 17 and 24 lbs.
Average weight. The average weight for a 1 year old child in the U.S. Would be between 22 and 25 pounds approximately. .