Height Calculator Based on Parents

Parental heights offer one of the earliest and most accessible clues about a child's potential adult stature. This calculator uses the mid-parental height formula — a straightforward method used by pediatricians worldwide — to estimate a child's genetic height target based solely on the mother's and father's heights. If you already have your child's current age, height, and weight measurements, our primary Height Calculator offers a more comprehensive estimate using the Khamis-Roche method.

How to Calculate a Child's Height Based on Parents

This tool requires only three inputs, making it the simplest height predictor on this site:

1. Select biological sex — Choose whether you are estimating for a boy or a girl. The formula differs for each.
2. Enter the mother's height — Use the biological mother's standing height in centimeters. If you know the value in feet and inches, convert it to centimeters first.
3. Enter the father's height — Use the biological father's standing height in centimeters.
4. Click "Calculate Height" — The result shows a genetic target height and a range representing normal variation.

Because this method does not use the child's current age or height, it can be applied before a child is born or at any point during childhood. Age-aware estimation methods also factor in the child's current measurements.

Mid-Parental Height Formula for Boys and Girls

The mid-parental height method has been used in pediatric practice for decades. Its core logic is simple: a child's expected adult height is closely related to the average of both parents' heights, adjusted for sex.

Formula for boys

Target height = (Mother's height + Father's height) ÷ 2 + 6.5 cm

The +6.5 cm (approximately 2.5 inches) accounts for the fact that, on average, adult men are about 13 cm taller than adult women. Since the mother's height brings down the average, the adjustment compensates for a male child.

Formula for girls

Target height = (Mother's height + Father's height) ÷ 2 − 6.5 cm

The −6.5 cm adjustment works in the opposite direction. Since the father's height raises the average, the subtraction accounts for a female child's expected stature.

The ±5 cm range

Clinicians typically add a ±5 cm (about ±2 inches) window to the calculated target. This 10-cm band reflects the reality that even children with identical parents do not end up at exactly the same height. Genetic recombination, epigenetics, and environmental factors all introduce variation.

How Genetics Influence a Child's Adult Height

Research estimates that 60–80% of the variation in adult height within a well-nourished population is attributable to genetics. However, height is not determined by one or two genes — it is a polygenic trait, meaning hundreds of genetic variants each contribute a small effect.

• Additive effects — Most height-related gene variants contribute independently. A child inherits a random combination from each parent, which is why siblings can differ by several centimeters.
• Dominant and rare variants — Certain rare genetic mutations can have large effects on height, either positive or negative. Conditions like Marfan syndrome (associated with tall stature) or achondroplasia (a form of dwarfism) are examples.
• Epigenetics — The way genes are expressed can be influenced by prenatal environment, maternal nutrition, and other factors, adding another layer of variation beyond the DNA sequence itself.

The mid-parental formula captures the net genetic signal effectively but cannot model these finer details. For that reason, it works well as a population-level estimate rather than a precise individual prediction.

Understanding the Child's Estimated Height Range

When the calculator displays a result like "172.0 cm (range: 167.0–177.0 cm)," it communicates two distinct pieces of information:

• The central target (172.0 cm) — This is the single most likely value given the parents' heights. Think of it as the peak of a probability distribution.
• The range (167.0–177.0 cm) — This represents the zone in which the large majority of children with these parental heights would end up. A few children will naturally fall outside this range.

The range is not a ceiling or a floor. A child who reaches 179 cm despite a target of 172 cm is not unusual — they may have inherited a particularly favorable combination of height-related gene variants, or they may have benefited from excellent nutrition and health during their growth years.

Similarly, a child who reaches only 165 cm is not necessarily unhealthy. The mid-parental target is a statistical average, not an individual guarantee.

Why Children May Be Taller or Shorter Than Their Parents

It is common for a child's adult height to differ noticeably from either parent's height. Several mechanisms explain this:

• Regression to the mean — Very tall parents tend to have children who are tall but slightly shorter than them, and very short parents tend to have children slightly taller than them. This statistical tendency pulls the next generation's height closer to the population average.
• Generational nutrition improvements — Children who grow up with better nutrition and healthcare than their parents did may exceed the mid-parental prediction. This secular trend has been observed worldwide over the past century.
• Genetic recombination — Each child receives a unique combination of their parents' genes. Two siblings can inherit different sets of height-influencing variants, producing meaningfully different adult heights from the same two parents.
• Health history — A parent whose own growth was limited by childhood illness, malnutrition, or untreated hormonal conditions may have a genetic potential taller than their actual measured height. In such cases, the mid-parental formula may underestimate the child's target.

How Accurate Is a Parent-Based Height Calculator?

The mid-parental height method is a well-established clinical screening tool, but its accuracy has known boundaries:

• Correlation with actual adult height — Studies show the mid-parental target correlates moderately well (r ≈ 0.40–0.50) with actual adult height. This means it captures a meaningful signal but leaves a substantial portion of variation unexplained.
• Error margin — For any individual child, the prediction may differ from actual adult height by 5–10 cm. The ±5 cm range captures most but not all outcomes.
• Best uses — The method is most valuable as a quick, no-measurement-needed benchmark for setting general expectations. It is especially useful before a child is born or during early childhood when growth data is limited.
• Limitations — It does not account for the child's current growth pattern, bone age, puberty timing, or health conditions. For a more refined prediction, clinicians may use bone-age X-rays, serial growth chart measurements, or methods like the Khamis-Roche equation that incorporate the child's own data.