| | Family Health | Pediatrics What is the average height of a 3 and half year old boy? According to the World Health Organization (WHO), the average height for a 3 and half year old boy is 98.7 cm (38.9 inches). Pediatrics - Related Articles The COBRA Act How to Modify a Wheelchair Properties of Aloe Vera Gel What Does the Cactus Cleanse Do? Can a tetanus shot prevent rabies? Treatment of Bunion Hallux Valgus Holistic Liver Detox