# 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).