The average newborn is 19.5 inches long and weighs 7.25 pounds. Boys have a head circumference of about 13.5 inches and girls measure in at 13.3 inches, according to the National Center for Health Statistics.
Birth to 4 Days Old
A baby drops 5 to 10 percent of his total body weight in his first few days of life because of the fluid he loses through urine and stool, says Parents advisor Ari Brown, M.D., author of Baby 411.
5 Days to 3 Months
Babies gain about an ounce a day on average during this period, or half a pound per week, and they should be back to their birthweight by their second-week visit. Expect a growth surge around 3 weeks and then another one at 6 weeks.
3 Months to 6 Months
A baby should gain about half a pound every two weeks. By 6 months, she should have doubled her birthweight.
7 Months to 12 Months
A child is still gaining about a pound a month. If you're nursing, your baby may not gain quite this much, or he may dip slightly from one percentile to another on the growth chart. "At this point, babies may also burn more calories because they're starting to crawl or cruise," says Tanya Altmann, M.D., a Los Angeles pediatrician and author of Mommy Calls. Even so, by the time he reaches his first birthday, expect him to have grown 10 inches in length and tripled his birthweight and his head to have grown by about 4 inches.