A 6-week-old should weigh between 8 pounds 4 ounces and 11 pounds 9 ounces, according to Parents magazine and KidsHealth. A 6-week-old baby gains about 1 ounce of weight per day for the first month, and then 5 to 7 ounces per week from one month to six months.
The range of weights is based on several factors. Normal full-term babies weigh between 5 pounds 8 ounces and 8 pounds 13 ounces, notes KidsHealth. Babies then gain 30 ounces in one month, or 1 ounce per day, to make a range of 7 pounds 6 ounces to 10 pounds 11 ounces.
Babies gain another 10 to 14 ounces within two weeks after reaching the first month of life, according to Parents. This final calculation determines the normal ranges of baby weights for 6-week-olds. At this point, babies should consume breast milk or formula eight to 12 times per day. This amounts to a feeding once every two to three hours.
Babies grow rapidly from seven to 10 days old, and then again from three to six weeks, according to KidsHealth. A normal newborn loses 7 to 10 percent of birth weight, or a few ounces, due to fluid loss in the first few days of life. The baby regains that weight within the first two weeks.