A healthy weight and height for children differs based on a number of factors, including gender and years or months of age. The University of Michigan suggests that the percentile a child falls into is not so important; rather, pay attention to whether the child is following a steady growth curve.
There are many online height and weight calculators for children, as well as growth charts, that indicate whether a child is within the healthy range. KidsGrowth asserts that weighing and measuring a child through the first three years is a key indicator of his overall health. Following a growth chart as a benchmark for monitoring a child's development is helpful; however, keep in mind that charts are created by using a statistical sample representing the whole population. The purpose is to represent the curve of a normal growth pattern. There is a wide variation in the height and weight of "normal" children. If a child had a premature birth or other special medical considerations, the growth chart may not be relevant.
BabyCenter recommends using the World Health Organization's chart for the first two years, and the Centers for Disease Control and Prevention chart for ages 2 and beyond. Consult a family doctor for questions about a child's specific growth progress.