Height calculator

What is a height calculator?

Predicting a child’s future height is a topic of constant interest for parents and researchers alike. The height calculator is based on scientific methods and studies, such as the Khamis-Roche method, which provides approximate adult height values based on the data of the parents. Let’s take a closer look at how this calculator works, what formulas are used, and what factors can influence the accuracy of forecasts.

A height calculator is a tool that predicts the likely height of a child based on their parents’ height and the child’s gender. Relying on statistical data and research, this tool is increasingly used by parents and healthcare professionals. It offers insights into possible height ranges, which can be useful for planning a child’s nutrition, physical activity, and other developmental factors.

The Khamis-Roche method

The classical method upon which many height calculators operate was proposed by Khamis and Roche in their paper, “Predicting adult stature without using skeletal age: the Khamis-Roche method,” published in 1994. This method does not require skeletal age data, simplifying the prediction process and making it widely accessible.

Khamis and Roche conducted an in-depth study examining the growth of children and adults using data from the Fels Longitudinal Study. Their method involved using the child’s anthropometric data (such as current height and weight) combined with parental height to predict adult stature. This approach proved effective across various populations, demonstrating considerable accuracy without the need for X-ray evaluations to determine skeletal age.

Calculation formulas

The height calculator uses two main formulas to predict a child’s future height:

1. Classical calculation

This formula is based solely on the height of the parents:

• For Boys:

  $\text{Predicted Height} = \frac{\text{Father's Height} + \text{Mother's Height} + 5.1}{2}$

• For Girls:

  $\text{Predicted Height} = \frac{\text{Father's Height} + \text{Mother's Height} - 5.1}{2}$

2. Adapted calculation

Adapted calculation takes into account parameters such as the child’s weight, height, and age, starting from four years old, as calculations before this age are not very informative. This calculation is most applicable to children of Caucasian descent as the studies were based solely on children of this race. Details of the study can be found here.

The adapted calculation applies specific coefficients and is generally considered more accurate than the classical one, though it still cannot provide definitive results. For instance, while the margin of error for the adapted calculation is typically +/-1.6-2.0 inches, the margin for the classical calculation can start at around 3.9 inches either upwards or downwards.

Examples of calculation

Example 1: Classical calculation

Suppose the father’s height is 70.9 inches, and the mother’s height is 66.9 inches. We can predict the height for a boy and a girl.

For a boy:

$\text{Predicted Height for a Boy} = \frac{70.9 + 66.9 + 5.1}{2} = \frac{142.9}{2} = 71.45 \text{ inches}$

For a girl:

$\text{Predicted Height for a Girl} = \frac{70.9 + 66.9 - 5.1}{2} = \frac{132.7}{2} = 66.35 \text{ inches}$

Example 2: Adapted calculation

If we take the same data from the classical calculation, where the father’s height is 70.9 inches, the mother’s height is 66.9 inches, and assume the 12-year-old child is 61 inches tall and weighs 90 pounds, then the predicted adult height would be 72.4 inches for a boy and 66.9 inches for a girl.

Growth charts

Growth charts are often used to assess and understand the growth of children, allowing comparisons with average values for their age.

Average height values for boys

Age	Average Height (cm)	Average Height (inches)
4	102	40.2
6	115	45.3
8	128	50.4
10	138	54.3
12	149	58.7
14	162	63.8
16	173	68.1

Average height values for girls

Age	Average Height (cm)	Average Height (inches)
4	101	39.8
6	114	44.9
8	126	49.6
10	137	53.9
12	150	59.1
14	159	62.6
16	162	63.8

Frequently asked questions

What height will a girl have if her father is 68.9 inches and her mother is 63 inches?

$\text{Predicted Height} = \frac{68.9 + 63 - 5.1}{2} = \frac{126.8}{2} = 63.4 \text{ inches}$

Does a child’s weight affect height prediction?

Weight may have an impact in adapted calculation methods, but it is not considered in the classical method.

Can this method be used for different ethnic groups?

The Khamis-Roche method was developed using data from a specific population, and its accuracy may vary based on ethnic and genetic differences.

How accurate are these predictions?

Predictions are approximate and based on statistical analysis. Individual variations can lead to differences in results.

Can the calculator be used for children of various ages?

Yes, the calculator can be used for various ages. However, the adapted calculation that considers a child’s weight, height, and age is better suited for children starting from four years old.

When do boys and girls stop growing?

Typically, girls reach their final height by 16-17 years old, while boys continue growing until about 18-19 years. These ages can vary depending on numerous factors, including genetics and lifestyle.

Thus, the height calculator allows parents and professionals to estimate the child’s likely adult height based on genetic and some biometric data. However, the final result depends on many factors, often not accounted for in simple formulas, such as the environment and individual characteristics of the child. Remember, these calculations are approximate even though they are based on scientific research.