The average weight of a 15-month-old girl is about 9.53 Kilogram. Boys of the same age weigh about 9.98 Kilogram. The average height for boys and girls at 15 months old is 31 inches.
Not All Babies are the Same
Just like adults, babies come in all shapes and sizes. Not all 15-month-olds will be the average weight for their gender. Some may be 2 or 3 pounds more and some 2 or 3 pounds less. Chubbiness or thinness at this age really doesn't matter as long as your baby is growing at a consistent rate.
According to KidsHealth.com, a website from the Nemours Foundation, a non-profit organisation devoted to improving the health of children, "A baby who is happy, active, and interested in nearby surroundings most likely is getting enough to eat and growing properly. A heavier child should not be put on a calorie-restricted diet without specific medical advice and supervision."