What this Mid-Parental Height Calculator does
The Mid-Parental Height Calculator estimates a child's target height from the heights of both parents. It uses a simple family-based formula: add the parents' heights, apply an adjustment based on the selected child sex, then divide by two. The result is shown in centimeters as an estimated target height.
This estimate can help families understand one way clinicians discuss inherited growth patterns. It is a broad reference point derived from parental heights. It does not tell you exactly how tall a child will be, when a growth spurt will happen, or whether a child's growth is healthy. Children inherit many traits from across their families, and their growth is affected by a range of biological and environmental factors.
The calculator uses the conventional adjustment of plus 6.5 cm for a boy and minus 6.5 cm for a girl before dividing by two. This convention is a simplified model. The displayed result should be treated as an estimate, rather than a target a child is expected to reach. A child's own measurements over time provide different information from a calculation based on parents.
How to use the Mid-Parental Height Calculator
Enter the mother's height and father's height in centimeters. Choose the listed sex adjustment that corresponds to the convention you want the calculator to apply. The first option is for a boy, and the second is for a girl. The calculator adds the selected adjustment to the sum of the two heights and divides the total by two.
For example, with a mother who is 165 cm tall and a father who is 178 cm tall, choosing the boy adjustment gives this calculation:
- 165 cm + 178 cm + 6.5 cm = 349.5 cm
- 349.5 cm ÷ 2 = 174.75 cm
- Rounded to one decimal place, the estimated target height is 174.8 cm
With the same parental heights and the girl adjustment, the calculation is (165 + 178 − 6.5) ÷ 2, which equals 168.25 cm, or 168.3 cm when rounded to one decimal place. These outputs illustrate how the adjustment changes the arithmetic. They do not establish an individual child's expected adult height.
Use height measurements in centimeters, and check that you have entered the parents' heights in the correct fields. The calculator accepts values within its displayed ranges. If a height is recorded in another unit, convert it to centimeters before entering it. Avoid using a child's current height as a substitute for either parent's height.
How the Mid-Parental Height Calculator formula works
The formula is (mother's height + father's height + sex adjustment) ÷ 2. The adjustment is +6.5 cm for the boy option and −6.5 cm for the girl option. Averaging the adjusted total gives the estimated target height in centimeters. The result is rounded to one decimal place for display.
In the worked example, the two parental heights total 343 cm. Adding 6.5 cm produces 349.5 cm, and dividing by two gives 174.75 cm. The calculator displays 174.8 cm. The arithmetic is transparent, but the formula itself is a population-based rule of thumb. It does not include a child's age, present height, growth history, health, or puberty timing, and it cannot account for all inherited variation.
The calculator produces one estimate, not a confidence interval or a guaranteed adult measurement. A single decimal place is a display convention and should not be mistaken for clinical precision. Small differences in measurement technique or rounding can shift the inputs and therefore the output.
Use cases for a mid-parental height estimate
Families may use a mid-parental height estimate as a starting point for learning about how parental heights can inform a broad discussion of growth. It can also make the underlying arithmetic easier to understand when a pediatric clinician introduces the concept. The result may prompt useful questions about how growth is measured and followed over time.
For a family discussing a child's development, useful questions can include:
- How does the child's height change across repeated measurements?
- How are age and growth history considered alongside family heights?
- What should we do if measurements seem inconsistent or concerning?
The estimate works best as context for a conversation. It is not a screening result and should not be used to diagnose a growth condition, set expectations for a child, or make decisions about treatment. Children's growth varies, and family comparisons can be emotionally sensitive. It may help to focus on the child's wellbeing and measured growth pattern rather than treating a number as a goal.
Other factors to consider when calculating a child's height
Parental height is only one piece of a child's growth story. Inherited variation comes from many relatives and genetic combinations, so a child may not follow the simple average suggested by two parental measurements. Health, nutrition, chronic conditions, and the timing of puberty can also influence growth. The calculator does not assess any of these factors.
Growth is usually understood through measurements collected over time and interpreted in context. A clinician may consider the child's age, growth pattern, family history, and overall health. One measurement or one calculator result cannot show whether a child is growing as expected. If you have concerns about growth, speak with a pediatric healthcare professional who can review the child's history and measurements.
Measurement quality matters, too. Height can vary with posture, equipment, and how a measurement is taken. If you are entering parental heights from memory, the result may differ from one based on carefully measured values. Treat any output as approximate, and do not compare it too closely with a child's future height.
Frequently asked questions
Is the estimated target height a prediction?
No. It is a rough estimate from parental heights and a conventional adjustment. It cannot predict an individual child's final height or replace growth assessments by a clinician.
Why does the calculation use a different adjustment for boys and girls?
The standard formula applies plus 6.5 cm for a boy and minus 6.5 cm for a girl before averaging. These are conventional values used in the simplified model, not a complete account of a child's biology or identity.
Can I enter heights in feet and inches?
This calculator expects centimeters. Convert each parental measurement to centimeters first, then enter it in the matching field. Mixing units would make the arithmetic incorrect.
What if my child's height is far from the estimate?
The estimate is not a required height or a threshold. Children can differ from it. If you are concerned about your child's growth or measurements, discuss the pattern with a pediatric healthcare professional.
Does this calculator account for age or current height?
No. It only uses the two parental heights and the selected adjustment. Age, current height, growth history, health, and puberty timing are outside this calculation.