The Khamis-Roche mid-parental height formula — the method used here — is one of the most studied height predictor methods available. Research shows it predicts adult height to within approximately 2 inches (5 cm) about 85–90% of the time. The remaining variation is explained by nutrition, overall health during childhood, and the complex polygenic nature of height inheritance. It is the standard used by many paediatricians for a childhood height predictor estimate.

The mid-parental height formula calculates a child's predicted adult height based on both parents' heights. For boys: (Father's height + Mother's height + 5 inches) ÷ 2, with a ±2-inch range. For girls: (Father's height + Mother's height − 5 inches) ÷ 2, with a ±2-inch range. The formula works in the metric system too (add/subtract 13 cm instead of 5 inches). This is the basis of the calculate mid parental height approach used by paediatricians worldwide.

This is a future height predictor based on the best-available non-clinical formula. However, no height prediction tool is "100% accurate" — including medical X-ray bone age assessments. Genetics accounts for roughly 80% of height variation, with the remaining 20% influenced by nutrition, sleep, health conditions, and hormones. For a 100% accurate height predictor, no such thing exists — but this calculator gives a well-researched and clinically used estimate.

Eye color is primarily controlled by the amount of melanin in the iris, which is regulated by several genes — particularly OCA2, HERC2, SLC24A4, and others. Brown eyes result from high melanin production and are generally dominant. Blue eyes indicate low melanin and are typically recessive. Green and hazel fall between. Our genetic eye color calculator uses a simplified model — real-world outcomes can vary because multiple genes interact in complex ways. Babies are often born with blue eyes that later darken.

Hair color is determined by the type and amount of melanin produced: eumelanin (brown/black) and pheomelanin (red/blonde). The MC1R gene plays a key role — red hair requires two copies of a recessive MC1R variant. Dark hair generally dominates over lighter shades. If both parents carry recessive blonde or red gene variants, a light-haired child is possible even from two dark-haired parents. Hair color can also change during childhood — many blonde babies develop darker hair by adolescence.

ABO blood type is inherited from both parents through a straightforward genetic system. Type O is recessive — both genes must be O to have type O blood. Type A and B are co-dominant, meaning AB individuals carry one A and one B gene. The blood type inheritance calculator maps all possible genetic combinations from both parents to show which ABO blood types the baby could inherit. The Rh factor (positive/negative) is separately inherited, with Rh-positive being dominant over Rh-negative.

Yes — our pediatric height predictor works for any age by combining the mid-parental height formula with the child's current height if you provide it. For very young children (under 2 years), current height is a less reliable indicator of adult height, as growth in infancy is highly influenced by nutrition rather than genetics. The mid-parental formula alone is often more reliable than current height for predicting the long-term adult height of toddlers and young children.

Yes — both can happen. Height does not always follow a simple average of the parents. Because height is polygenic (controlled by over 700 identified gene variants), children can inherit a combination that results in them being taller or shorter than either parent. A child can be taller than both parents if they happen to inherit more "tall" genetic variants from the grandparent or great-grandparent pool. The mid-parental height formula accounts for this through its ±2-inch prediction range.