According to the Centers for Disease Control and Prevention's Weight-for-age Percentile, the average weight of a 19-month-old boy is around 26 lbs. Doctors and other medical professionals have the correct equipment to determine your child's weight; a home scale may not be dependable.
Overweight and Underweight
If your son weighs over 30 lbs. at 19 months, he will be in the top 10 percent for toddlers his age. He will be in the bottom 10 percent if he weigh less than 23 lbs. at 19 months. Those with concerns about a child's weight should contact a physician.
Should your child be far from average weight for someone of his age, it is important not to panic. The Centers for Disease Control and Prevention says that "to help your child maintain a healthy weight, balance the calories your child consumes from foods and beverages with the calories your child uses through physical activity and normal growth."