by what percent does the average baby increase in length during the first year?
The average weight of a 6-month-old is about 16 pounds (7.3 kg), and the average weight of a 1-year-old is approximately 21Â½ pounds (9.8 kg). Boys may be bigger than girls, and breastfed infants may weigh less than formula-fed babies. Average Height of a Baby in First Year In general, during the first six months, a baby grows about one inch per month. Between 6 months and one year, it slows down a bit to about a Â½ inch per month.