Birth to 1 month: The average newborn gains 2/3 to 1 ounce a day and grows 1 to 1 1/2 inches in length over the course of the whole month. Remember that most babies lose some weight during the first few days of life, but usually regain this weight over the next few days so that within a week to 10 days they’re back to their original birth weight.
1 to 4 months: Babies usually gain 1 1/2 to 2 pounds and grow 1 to 1 1/2 inches each month. During this time, your baby may begin looking chubby; however as her activity level increases, those baby rolls will soon be replaced by developing muscle.
By 6 months: Most babies have doubled their birth weight.
By 12 months: Most babies have usually tripled their birth weight and will have grown 9 to 11 inches from their original birth length.
By 24 months: Most babies have quadrupled their birth weight and will have grown 14 to 16 inches from their birth length.
At each of your baby’s well visits your pediatrician will track your child’s weight, height, and head circumference on a growth chart. This standard chart was developed from data using national surveys and doctors use it to determine the progress your baby is making compared with other babies of the same age and sex. Many parents worry if their baby’s measurements are on the high or low end of the chart. While these concerns are normal, remember that your child’s percentile is not as important as the fact that she’s growing consistently. If your pediatrician isn’t concerned about your child’s size or growth patterns, you shouldn’t worry either.