In my previous post, I tried to take a guess at the thinking, intentions, rationalizations, justifications, and reasons why some people, mostly females, will always choose the taller mate partner if they had a choice in mate selection. Now, let’s see whether their choices will actually results in the tall or at least average size offspring they hope for.

In a previous post I had already written about the equations medical professionals use to calculate for the final height of the parents.

There is already many, many calculators online where you just enter the heights of one’s parents, age, sex, and the result of the child is easily produced. Places like Calculator.com, Parenting.com, Babycenter.com, or BBC UK all have the same calculator which probably use the same formula to calculate the child’s ultimate height. (haven’t tested that claim yet though).

It turns out that there is more than one type of equation the medical community has created and/or use to figure out children’s final height.

From the Mayo Clinic website with an answer by  Jay L. Hoecker M. D.

There’s no proven way to predict a child’s adult height. However, several formulas can provide a reasonable guess for child growth. Here’s a popular example:

• Add the mother’s height and the father’s height in either inches or centimeters.
• Add 5 inches (13 centimeters) for boys or subtract 5 inches (13 centimeters) for girls.
• Divide by two.

Most children will reach an adult height within 4 inches (10 centimeters) of this estimation.

Another way to estimate a child’s adult height is to double his or her height at age 2.

Remember, a child’s height is controlled by genetics. It’s also important to note that children grow at different rates. Some children begin their growth phases early, while others are late bloomers. If you’re concerned about your child’s growth, consult his or her doctor.

So the equation they gave for this was where x = father’s height, and y = mother’s height, ((x+y)+5)/2 for boys, and ((x+y)-5)/2 for girls. the deviation is extremely large, by over 4 inches, which I have found to be really large of a height distribution.

From the Family Practice Notebook website…

1. Step 1: Calculate Final Height prediction (mid-parental height)
   1. Boy
      1. In: (Father’s Height + Mother’s Height + 5) / 2
      2. Cm: (Father’s Height + Mother’s Height + 13) / 2
   2. Girl
      1. In: (Father’s Height – 5 + Mother’s Height) / 2
      2. Cm: (Father’s Height – 13 + Mother’s Height) / 2
2. Step 2: Identify Predicted Growth Percentile
   1. Use above predicted mean height to mark growth chartIdentify growth percentiles for the predicted height
      1. Mark chart at 18-20 year old mark
      2. Mark Confidence Interval s
         1. Mean Height in inches +/- 2 inches (some use 3.3 inches)
         2. Mean Height in centimeters +/- 5 centimeters (some use 8.3 cm)

What seems to be obvious is that the same formula has been used for this reference. the values of the father and mother are added up and a correct factor of 5 is either or subtracted due to gender, and the value is then divided in half. For inches to cm, the conversion is to multiply by 2. 55-2.66.

From another resource InteliHealth.com Robert H. Shmerling, M.D. answers the question “Can We Predict Height?”

• From infancy, when average length is 20 inches, to age 2 there is initially rapid growth, then slowing, with about 14 inches in height added.
• From age 2 to puberty there is slow, steady growth at about 2½ inches per year.
• As one enters puberty, a growth spurt of 3 to 5 inches in a year is common.
• By ages 40 to 50, height actually may begin slowly to decline, even in healthy adults.

A major determinant of height is how long the longest bones become, such as the femur (in the upper leg), tibia and fibula (in the lower leg)….The growth spurt around the time of puberty occurs two years earlier in girls when compared with boys, but the boys tend to be taller when it begins. Most of the average height difference between adult men and women (about 5 inches) relates to the greater growth of boys during the adolescent growth spurt and the greater height achieved prior to that growth spurt (even though girls tend to start their growth spurt sooner)….Rather predictably, we achieve about half of our adult height by age 2. So one way to predict ultimate height is simply to double the height achieved by the second birthday.

One commonly quoted formula uses parental height and gender to predict adult height (in inches) as follows:

   For men: (height of mother + height of father + 5)/2
   For women: (height of mother + height of father – 5)/2

If you know your parents’ heights, see if this formula predicts yours well; for most people, this will accurately predict your height within 2 or 3 inches.

All of these methods can only approximate ultimate height; they cannot predict with precision. In addition, formulas and growth charts to predict height are based on large numbers of normal children and do not perform well in predicting the ultimate height of an individual child who is unusually short or tall, has been ill, or has a genetic disorder.

Conclusion: I think at this point from three references, there is one general formula most pediatricians who are asked this type of question by concerned parents will use. It is simple, easy to calculate, and has a height range of 6-8 inches. I think the key thing to take away is to see that on average, the children of short people who marry and mate with tall people end up slightly taller than their parents of the same gender and end up somewhere in either the middle to the taller range. Overall, the results are a bad indication of what final height the children ill end up since there is so much room for deviation. I’ve known children of tall parents who end up shorter than both of them, and i’ve seen even more cases of children who end up even 1 feet taller than their parents. The answer is that an endocrinologist or pediatrician can definitely calculate a value for the child but most likely that value will be off so it is possible to get a very weak guess at the right value of the final height.