Height Predictor

The predictor gives a child's mid-parental height, sometimes called the target height: an estimate of adult height built only from the heights of the two parents. It is the simplest published way to answer "how tall will my child be?" and it is the method the American Academy of Pediatrics describes for parents. HeightViz applies that method exactly as written, shows the margin the source states, and stops there. It does not look at the child's current height, age or growth so far.

Because it is an average of two heights with a fixed adjustment, the estimate is the same for every child of the same two parents and the same sex. It describes what is typical for children of parents those heights, not what any one child will reach.

The method adjusts one parent's height by 5 inches (12.7 cm) and then averages the two heights. For a boy, 5 inches are added to the mother's height before averaging with the father's. For a girl, 5 inches are subtracted from the father's height before averaging with the mother's. The two estimates for the same parents therefore sit exactly 12.7 cm apart.

Worked example with the page's starting heights, the sourced average US adult woman (161.3 cm (5'4")) and man (175 cm (5'9")): for a boy, (161.3 cm + 12.7 cm + 175 cm) ÷ 2 = 174.5 cm (5'9"). For a girl, (175 cm − 12.7 cm + 161.3 cm) ÷ 2 = 161.8 cm (5'4"). Heights typed in feet and inches or metres are converted to centimetres at exactly 2.54 cm per inch before the arithmetic, so the result does not depend on the unit used.

The source gives a margin of error of about 4 inches (10.2 cm) up or down, and the page shows that range beside every estimate: for the boy in the example, 164.3 cm (5'5") to 184.7 cm (6'1"). A range that wide is the honest answer. Adult height is shaped by many genes, not only the ones visible in two parents' heights, and by nutrition, health during childhood and the timing of puberty. Two children of the same parents can finish at quite different heights, and some land outside the stated margin.

Treat the number as a rough expectation, the kind a paediatrician might mention in conversation, rather than a prediction to plan around. The predictor never rounds the estimate toward a rounder or more pleasing figure.

The board below the result draws the mother, the father and a figure at the estimated adult height on one scale, with a centimetre ruler on one side and a feet-and-inches ruler on the other. It is the same comparison engine as the height comparison board, so the estimated figure is exactly as tall relative to the parents as the numbers say. The range is not drawn, because a figure can have only one height; the numbers above the board carry it.

To see how far apart two of the heights are in every unit, open the height difference calculator. To put the estimate beside adults in a particular country, the average height by country pages open a board with each country's sourced figures.

The mid-parental method knows nothing about the child. It does not use the child's current height, weight or age, how fast they have been growing, or whether puberty has started, and it cannot detect any condition that affects growth. Clinicians assess growth with age- and sex-specific growth charts, repeated measurements over time and, where needed, further tests; none of that happens here. If a child's growth is a concern, that is a question for a clinician, not for a calculator.

The heights you enter stay in your browser and nothing you type is stored. A shared link carries the two heights, the boy or girl choice and the unit in the link itself, so opening one sends those values to our server as part of the web address.

• American Academy of Pediatrics, HealthyChildren.org: How Tall Will My Child Be? Predicting a Child's Adult Height — Mid-parental method. Boys: [(mother's height + 5 inches) + father's height] ÷ 2. Girls: [(father's height − 5 inches) + mother's height] ÷ 2. "You can expect a margin of error of about 4 inches up or down." By Adriana Maria Tavares Gomes, MD and Lynne M. Bird, MD, FAAP; page last updated 16 September 2026. Checked 2026-09-20.