Standards for height and weight of one-year-old and two-year-old babies. When a baby is two years old, height and weight are important indicators to evaluate whether its growth and development are normal. According to the standards issued by the World Health Organization (WHO), the average height of a two-year-old boy is 86.7 cm and weight of 12.3 kg; the average height of a two-year-old girl is 85.1 cm, with a weight of 12.3 kg.