Child Height Calculator

Will your child be tall like dad, petite like mum, or somewhere happily in between? The Child Height Calculator at the top of this page answers that question with the best-known everyday method: it predicts a child's adult height from the heights of both parents, adjusted for whether the child is a boy or a girl.

The method is called mid-parental height, and paediatricians have used it for decades as a first estimate when parents ask how tall a child will be. It is simple, it is honest about its limits, and it gives you a likely landing zone rather than a false promise of an exact final number.

On this page you will find what the calculator does, the ideas that make it work, clear steps for using it, two fully worked examples for a boy and a girl, background on how children grow, practical tips, and fifteen frequently asked questions. In a few minutes you will have your estimate and a clear sense of how much weight it deserves.

What Is the Child Height Calculator?

The Child Height Calculator is a free online tool that estimates a child's final adult height. You enter the father's height in inches, the mother's height in inches, and the child's sex, and it returns the predicted adult height in inches and feet and inches, plus a likely range with a low end and a high end about 2 inches either side of the prediction.

For a boy, the formula adds the father's height and the mother's height, adds 5 inches, and divides by two. For a girl, it adds both heights, subtracts 5 inches, and divides by two. The 5-inch adjustment reflects the average difference between adult men and women, letting both parents' heights be averaged on the right scale for the child's sex.

The output is an estimate built on family pattern, not a measurement of your individual child. It knows nothing about your child's current height, growth rate, health, or puberty timing, so it should be read as the centre of a probable range. Most children finish within about 2 inches of it, and nearly all finish within about 3.5 inches.

The Key Ideas Behind the Prediction

The first idea is that adult height is mostly inherited. Between 60 and 80 percent of the difference in height between adults is explained by genes, which is why the heights of the two parents carry so much predictive power. A child is, genetically, a fresh shuffle of both parents' growth instructions.

The second idea is the sex adjustment. Men average roughly 5 inches taller than women in most populations. Predicting a daughter from her father's height without shrinking it to a female scale would overstate her height, and predicting a son from his mother without the opposite adjustment would understate his. The plus-or-minus 5 inches keeps the maths fair.

The third idea is regression toward the family centre. Very tall couples tend to have children slightly shorter than the taller extremes in the family, and very short couples tend to have children slightly taller. Averaging the parents naturally builds in this gentle pull toward the middle, which matches what clinics observe.

The fourth idea is that the calculator reports a range for a reason. Siblings with the same parents routinely finish 2 to 4 inches apart. Nutrition, sleep, health, and puberty timing fill in the rest of the story, so a single precise-looking number would actually be the dishonest answer.

How to Use the Child Height Calculator

1. Measure or look up the father's height in inches, barefoot if possible, and type it into the first box.
2. Enter the mother's height in inches in the second box, measured the same way for a fair pairing.
3. Choose the child's sex from the dropdown, because the formula adds 5 inches for a boy and subtracts 5 inches for a girl.
4. Press Calculate to see the predicted adult height, plus the low and high ends of the likely range.
5. Read the result as a band, not a target: most children land inside the shown range, and landing anywhere inside it is completely normal.

Worked Example 1: Predicting a Son's Height

A father of 69 inches and a mother of 63 inches want to estimate how tall their young son will be as an adult.

The father's height is entered as 69 inches, which is 5 feet 9 inches.

The mother's height is entered as 63 inches, which is 5 feet 3 inches.

They select Boy, so the calculator adds the 5-inch adjustment.

The sum is 69 plus 63 plus 5, which equals 137.

Dividing 137 by 2 gives a predicted adult height of 68.5 inches, displayed as 5 feet 8.5 inches.

The likely range runs from 66.5 inches to 70.5 inches, so the family expects a son of roughly average adult height.

Worked Example 2: Predicting a Daughter's Height

A taller couple, a father of 72 inches and a mother of 65 inches, want the estimate for their daughter instead.

The father is entered as 72 inches, exactly 6 feet tall.

The mother is entered as 65 inches, or 5 feet 5 inches.

They select Girl, so this time the calculator subtracts the 5-inch adjustment.

The working sum is 72 plus 65 minus 5, which equals 132.

Dividing by 2 gives a predicted adult height of 66 inches, or 5 feet 6 inches.

Her likely range is 64 inches to 68 inches, tall for a woman, exactly as her parents' heights would suggest.

How Children Grow From Birth to Adulthood

Growth is fastest at the very start: babies typically add about 10 inches in the first year and another 5 in the second. Growth then settles into a steady childhood rhythm of roughly 2 to 2.5 inches a year, a calm period during which a child's rank among classmates stays fairly stable and family patterns become easy to spot.

Puberty restarts rapid growth. Girls usually begin their spurt between 9 and 12 and gain around 3 inches a year at its peak, while boys start later, between 11 and 14, and can gain 3 to 4 inches in their best year. Because girls start earlier, classes of 11-year-olds often show girls towering over boys who will eventually pass them.

After the spurt, growth slows as the growth plates at the ends of the long bones harden and close. Most girls reach their final height by about 15 or 16, roughly two years after their first period, and most boys by about 18. A few late maturers on both sides keep adding small amounts for a year or two longer.

Doctors track all of this on growth charts, and the pattern matters more than any single point. A child following their own curve steadily is growing healthily, wherever that curve sits. The parental prediction on this page complements the chart: the chart shows the journey so far, and the prediction sketches the likely destination.

How Accurate Are Parental Height Predictions?

Mid-parental height is the workhorse estimate of children's clinics because it is quick, free, and right more often than any other simple method. In practice, about two-thirds to three-quarters of children finish within roughly 2 inches of the prediction, and the great majority finish within about 3.5 inches of it. For a family conversation, that is usefully accurate.

The method's blind spots are worth knowing. It cannot see grandparents' genes that skipped a generation, it cannot know whether a child takes after the taller or shorter side, and it assumes average nutrition and health. A child recovering from a long childhood illness, or one with an untreated hormone issue, may fall short of the estimate for reasons the formula cannot detect.

More advanced clinic methods exist. A bone-age X-ray of the left hand shows how much growth remains in the skeleton, and combining bone age with current height produces a tighter forecast, especially for children approaching puberty. Growth specialists use these tools when a child's chart raises real questions, not for everyday curiosity.

For most families, the sensible approach is layered: use this calculator for the family expectation, track actual height twice a year, and let a doctor reconcile the two if they ever drift far apart. The estimate sets the expectation; your child's own steady curve confirms or corrects it over time.

One more habit is worth adopting while your child is young: keep a simple note of the prediction together with the dates and results of each twice-yearly measurement. When the two are read side by side over several years, you can see at a glance whether your child is strolling steadily toward the family range or drifting away from it, and that small record is exactly what a doctor wants to see at any growth review. It turns a one-off estimate into a living reference for the whole of childhood.

Practical Tips for Parents

1. Measure both parents honestly. Use barefoot heights against a wall; remembered heights from driving licences are often an inch too generous.
2. Convert carefully. Five feet eight inches is 68 inches, not 5.8 of anything. Multiply feet by 12, then add the inches.
3. Run it for each child separately. The sex adjustment changes the answer, so a son and a daughter of the same parents get different predictions.
4. Write the prediction down. Noting the estimate and range in your child's health record makes later growth checks easier to interpret.
5. Plot real growth twice a year. A wall chart or clinic record shows whether your child is tracking sensibly toward the family range.
6. Back growth with basics. Enough food, protein, calcium, vitamin D, sleep, and daily activity help a child reach the top of their range.
7. Avoid single-number thinking. A prediction of 68 inches means roughly 66 to 70 in real life. Anywhere in that band is a success.
8. Ask a doctor about big gaps. If your child's growth curve points far below the family range, a check-up can rule out treatable causes early.

Frequently Asked Questions

1. How accurate is the Child Height Calculator?

Most children finish within about 2 inches of the mid-parental prediction, and nearly all within about 3.5 inches. It is a clinic-grade first estimate.

Accuracy drops when a child's growth is affected by illness, hormone problems, or very unusual family patterns, such as one very tall grandparent.

2. What is mid-parental height?

It is the average of the two parents' heights after adjusting by 5 inches for the child's sex: plus 5 for a boy, minus 5 for a girl.

Clinics use it as the target height against which a child's actual growth is compared. This calculator automates exactly that method.

3. Why does the formula add or subtract 5 inches?

Adult men average about 5 inches taller than adult women, so parental heights must be shifted onto the child's sex scale before averaging.

Without the adjustment, sons would be under-predicted and daughters over-predicted by 2.5 inches each.

4. Does the calculator use my child's current height?

No. The prediction comes only from the parents' heights and the child's sex. Your child's present size does not enter the formula.

That is its simplicity and its limit. A doctor reviewing growth will also weigh the child's own measurements and growth rate.

5. What does the low and high range mean?

The range shows the prediction minus and plus about 2 inches. Most children finish inside this band.

Think of the headline number as the centre of the target and the range as the realistic spread for a normal, healthy child.

6. Can siblings get different predictions?

Yes, whenever their sexes differ, because the 5-inch adjustment flips direction between a son and a daughter.

Even same-sex siblings often finish inches apart, since each inherits a different mix of the family's growth genes. That is normal.

7. What if one parent's height is unknown?

You can substitute the height of a grandparent or adult sibling on that side, but treat the answer as rougher than usual.

If no stand-in exists, the other parent's adjusted height alone gives a very loose guide. Clinics face the same issue with adopted children.

8. When do children stop growing?

Most girls reach adult height by about 15 or 16, and most boys by about 18, when the growth plates in their bones close.

Late maturers may grow a little longer. A bone-age X-ray can show whether meaningful growth remains.

9. Can food or supplements beat the prediction?

Good nutrition lets a child reach their genetic potential, but no food or supplement pushes a healthy child beyond it.

Chronic under-nutrition can pull a child below the prediction, which is why adequate meals matter more than marketed height products.

10. Why is my child shorter than classmates?

Children start puberty at very different ages, so height rankings at 11 or 13 often reverse by adulthood.

Judge your child against the family range and their own growth curve, not against the tallest child in class this year.

11. Is a short predicted height a problem?

Not by itself. Short, healthy adults are a normal part of human variation, and the prediction simply reflects the family pattern.

Concern is warranted only when a child grows much more slowly than expected or falls away from their own curve.

12. How often should I measure my child?

Twice a year is plenty for a healthy child. More frequent measuring mostly captures posture and time-of-day differences.

Use the same wall, the same time of day, and no shoes, and write the date beside each mark or record.

13. What units does the calculator use?

Enter heights in inches. Results appear in inches, in feet and inches, and the range is given in inches as well.

To convert centimetres to inches, divide by 2.54. To convert feet and inches, multiply the feet by 12 and add the inches.

14. Can this calculator predict for adopted children?

Only if the biological parents' heights are known, since the method is entirely genetic. Adoptive parents' heights do not predict the child's growth.

For adopted children, doctors rely on the child's own growth chart and, when needed, a bone-age assessment instead.

15. When should I see a doctor about growth?

Book a review if your child grows less than about 2 inches a year in mid-childhood, falls across chart lines, or puberty is very early or has not started by 13 in girls or 14 in boys.

A doctor can check overall health, hormones, and bone age, and most causes of slow growth are easier to help when found early.

CONCLUSION

The Child Height Calculator gives you the same family-based estimate that children's doctors have trusted for years: a predicted adult height with an honest range around it. It takes under a minute and needs nothing but the two parents' heights.

Use it as a guide, not a verdict. Track your child's real growth twice a year, support it with food, sleep, and play, and the final height, wherever it lands in the range, will be the right one for your child.