Calculating your child's height is based on gender, the height of both of parents and the child's diet and activity level. A number of methods exist and none is definitive. However, it can be fun to guess what your child's height will be, and for some kids, it may be medically necessary. As long as you can track a few statistics, you can gauge the potential range for your child's full height.

Gather the required statistics. Your child's height and weight, age and gender are all required for the closest guess. Also write down the height of each parent.

Add the parents' heights together. If your child is a boy, add 5 inches and divide by two. This number is the estimated height for a boy. If your child is a girl, subtract 5 inches and divide by two. The result is the estimated height for a girl. Most children are within 4 inches of this number when they reach their full adult height.

Check your baby book. Another method of estimating height is to take your child's height at the age of 2 and simply double it. This estimate is less accurate than the calculation in Step 2, but it remains a popular approach.

Use an online tool. Many online sites include a calculator that uses the data to run the calculation for you. Note whether the site requires a specific age, as many height calculators assume a child is either over age 2 or 4, which can make a significant difference in the final number.

Have your child's wrist X-rayed. X-rays can determine with specificity your child's chronological age. This painless procedure evaluates the growth-plate status in your child's wrist compared to the range of normal development. Using this information, doctors can pinpoint any growth or hormone issues that may be emerging if your child's age and the maturation of her skeleton are at odds. It also helps doctors treat children who have conditions that may affect their growth.