| | Family Health | Pediatrics What is the Average height 3 year old boy in inches? The average height for a 3-year-old boy in the United States is 36.6 inches, according to the Centers for Disease Control and Prevention (CDC). Pediatrics - Related Articles How to Identify & Replace Negative Thinking Patterns What is the recommended temperature for a workplace? Herbal Treatment for Hernias How do you measure lung capacity? What Are the Benefits of Antioxidants on the Brain? Information About Bee Propolis EPA Priority Pollutants