# 3 ways to predict height

Will your son or daughter be a center in basketball or a jockey on racehorses? The answer is usually somewhere in between, but all parents (and children) are curious about the size of their children. Height is determined by genetics (70%) and environmental factors (30%) such as nutrition and exercise, and there are so many variables that predicting height cannot be an exact science. However, there are scientifically based methods that will give you a fairly accurate idea of how tall your child will be.

## Steps

### Method 1 of 3: Predict the child's final height based on the height of the parents

#### Step 1. Use Gray's method for unborn children up to four years old

This involves combining the heights of the parents, with a modification according to the child's sex (the half-parent rule), and dividing the amount by two.

• This method is derived from an article by Horace Gray published in 1948 in the journal Child Development, which has been widely used until now.
• The margin of error is +/- 10 cm (4 inches), which might seem like a lot (think about the difference between measuring 160 cm, or 5 feet 2 inches, and 180 cm, or 5 feet 10 inches), but which demonstrates how difficult altitude forecasting is due to its many variables.

#### Step 2. Measure the height of the father and mother

This method works with inches or centimeters.

#### Step 3. For a girl, decrease the father's height by thirteenth (12/13 of the height)

In the case of a child, the mother's height increases by one thirteenth (13/12 of the height).

• For example, if the girl's father is 69 inches (175 cm), multiply that by 12 and divide by 13, and you get the modified height of 63.7 inches (161 cm).
• Similarly, if a child's mother is 63 inches (160 cm), multiply by 13 and divide by 12, and you get the modified height of 68.3 inches (173 cm).

#### Step 4. Add the modified height of one parent with the unmodified height of the other

In the example of the girl who has a father who is 175 cm (69 inches) who was changed to 161 cm (63.7 inches) and a mother who is 160 cm (63 inches), the sum will be 321 cm (126.7 inches).). For the male child, the operation will be 175 cm (69 inches) for the father + 173 cm (68.3 inches) for the modification of the mother = 348 cm (137.3 inches).

#### Step 5. Divide the sum by two to find the child's final height

Use the examples from the last step. In Example 1 (girl), divide 321 cm (126.7 inches) / 2 = 161 cm (63.5 inches). In Example 2 (male child), it will be 348 cm (137.3 inches) / 2 = 174 cm (68.7 inches).

#### Step 6. Put it all together

Thus, a girl whose father is 69 inches (175 cm) and her mother is 63 inches (160 cm) is predicted to be 63.5 inches (161 cm). Similarly, it is predicted that a child with parents of the same height can grow to be 174 cm (68.7 inches).

• These are the formulas in inches: ((69 x 12/13) + 63) / 2 = 63.3 [girl]; (69 + (63 x 13/12)) / 2 = 68.7 [child].
• There are also web pages that will do the calculations for you if you enter the heights they ask for.
• Remember that, with the precision range of this method, the girl in the example can be reasonably expected to be between 151 cm and 171 cm (59, 3 and 67.3 inches), based on the factors of environment and of genetic variation.

#### Step 7. Use simpler variations, if you prefer

There are variations of Gray's method that omit the 12/13 modification and simply add the heights of the two parents and divide by 2, then add 3 or 5 inches (7 or 15 cm) to the result for a child or subtract the same amount in the case of a girl. The results will be very close to the original method.

• Therefore, in the case of a girl, the formula will be like this in inches: ((69 + 63) / 2) - 3 = 63 inches or ((69 +63) / 2) - 5 = 61 inches.
• For a child, it will be as follows: ((69 + 63) / 2) + 3 = 69 inches or ((69 + 63) / 2) + 5 = 71 inches.

### Method 2 of 3: Predict the final height based on the child's current height

#### Step 1. Double the height of a girl when she is 18 months old or a boy when she is 2 years old

This is probably the simplest method and is strictly based on the height of the child at a young age.

• For example, you can predict that a girl who is 81 cm (32 inches) tall at 18 months will reach 162 cm (64 inches or 5 feet 4 inches), while a boy who is 91 cm (36 inches) tall Height at 2 years will reach 182 cm (72 inches or 6 feet).
• The margin of error of +/- 10 cm (4 inches) also applies to this method.

#### Step 2. Use the Khamis-Roche method

This method is derived from an article published in 1994 in a magazine and is based on a more complex scale of equations based on six factors: the sex of the child, the height of the mother, the height of the father, the height of the child, the child's weight and child's age.

• This method is recommended for children 4 years of age and older.
• Unless you want to test your math skills, do the math with an internet calculator.
• For example, a 40-inch, 45-pound (101 cm), 4-year-old girl with a 63-inch (160 cm) mother and 69-inch (175 cm) father can be predicted to reach measure 160 cm (63 inches or 5 feet 3 inches).
• The 90% margin of error for this method is approximately 5 cm (2 inches). This means that 90% of children who meet the above criteria will grow to between 155 and 165 cm (61 and 65 inches).

#### Step 3. Have the child's “bone age” determined by X-ray

This method originated in 1959 and has been updated several times. This involves taking an X-ray of the child's left hand, fingers, and wrists, and comparing bone age with chronological age.

• Obviously, it is not a home method. Discuss your interest in this method with your child's doctor.
• This method is considered a bit more accurate (but not significantly) than the Khamis-Roche method.

### Method 3 of 3: Predicting Final Height for a Child Eight Years and Over

#### Step 1. Use what is sometimes called the “Lauren” method for women ages 8-16 and men ages 9-18

The Khamis-Roche and bone age methods can also be used for children in this age range.

• This method was launched in 2005 and uses the child's gender, date of birth, date of test, height, sitting height, and weight.
• There are calculators on the internet for this method as well.
• For example, a girl born on May 5, 2003, tested on May 5, 2015, is 160 cm (63 inches) tall, has a sitting height of 125 cm (49 inches), and 54 kg (120 pounds) could weigh up to 164 cm (64.7 inches or 5 feet 5 inches).

#### Step 2. Moderate your expectations, even for older children

Even if they are used in adolescents who are close to their final height, these methods have a margin of error. There are so many factors that influence the final height that no prediction method is completely accurate. Growth periods vary in occurrence and duration, environmental factors and so on can change. The only way to know for sure is to wait and see.