1. Weight and height development indicators The average weight of a six-month-old baby should be between 6.2-9.5 kg, and the average height should be between 61-70 cm. During this period, the baby\’s weight increases rapidly, approximately 150-200 grams per week. Height also grows rapidly, with an increase of about 2.5 centimeters per month. 2. Head circumference development indicators The average head circumference of a six-month-old baby should be between 41-46 cm. Head circumference is an important indicator of a baby’s brain development, so doctors often measure it.