The best way to answer your question is to turn to the standard growth chart your pediatrician has hopefully shown you during each of your well visits (or to one of the many smartphone apps now available that simply require you to enter in your child’s age and measurements before giving you the corresponding percentiles for height, weight, and head circumference). By simply entering your son’s age (3 months) relative to his height (26 inches), you’ll find that he actually is quite long for his age—measuring in at just above the 95th percentile. For comparison, the average length of a 3-month-old boy is 24 inches. This isn’t that surprising, given that he was also above average in height even when he was born, as 21 inches put him close to the 90th percentile—or longer than nine out of 10 newborn boys.
With all that said, the most important thing to remember about following a baby’s height and weight is that it’s not as important to focus any one set of measurements, but rather to watch to see that babies are following a healthy, predictable pattern of growth over time.