Height Calculator

The most common way to estimate a child's adult height is the mid-parental height formula, also called the Tanner method - and that is exactly what this height calculator uses. It takes the mother's and father's heights, averages them, and adjusts for the child's sex. For example, a boy whose mother is 5'4" and father is 5'10" has a mid-parental estimate of about 5'10" (176.68 cm), with a likely adult range of roughly 5'6" to 6'1". The calculator works in feet and inches or in centimeters, and shows the range as well as the single most-likely number.

It is worth being clear about what this is: an estimate based only on the parents' heights. It is not a medical prediction, and it cannot tell you when your child will reach their adult height. Think of it as a well-grounded ballpark - useful for satisfying curiosity, not for making decisions. For a real growth assessment, a pediatrician plots a child on the CDC growth charts over time, which this tool does not do.

How this height predictor works

A child's height is strongly influenced by the heights of their parents, because height is one of the most heritable human traits. The mid-parental method captures that link with a single, simple idea: a child tends to land near the average of their two parents, nudged up if they are a boy and down if they are a girl, because adult men are on average taller than adult women. The formula does not try to model nutrition, puberty, or health - it isolates the genetic signal that the parents' heights carry, and expresses the remaining uncertainty as a range.

The mid-parental height formula

The method uses one formula per sex, in centimeters:

The 13 cm (about 5.1 inches) is the average height gap between adult men and women. An equivalent way to see it: average the two parents' heights, then add 6.5 cm (about 2.5 inches) for a boy or subtract 6.5 cm for a girl - both give the same answer. Around that central figure, the likely range is about ±8.5 cm (±3.3 inches), and roughly 95% of children reach an adult height inside that band. To keep both unit systems consistent, this calculator does the math in centimeters and converts the result to the nearest whole inch for the feet-and-inches display.

Worked example: predicting a son's height

Suppose a mother is 5'4" and a father is 5'10", and you want to estimate their son's adult height.

1. Convert to centimeters: 5'4" = 64 in × 2.54 = 162.56 cm; 5'10" = 70 in × 2.54 = 177.80 cm.
2. Apply the boy formula: (162.56 + 177.80 + 13) ÷ 2 = 353.36 ÷ 2 = 176.68 cm.
3. Convert back: 176.68 ÷ 2.54 ≈ 69.6 in, which rounds to 70 in = 5'10".
4. Add the range: 176.68 ± 8.5 cm = 168.18 to 185.18 cm, or about 5'6" to 6'1".

So the son's most likely adult height is about 5'10", the same as his father here, and most likely somewhere between 5'6" and 6'1". Notice the son matches the taller parent because the boy adjustment (+6.5 cm) roughly cancels the gap between a 5'4" mother and a 5'10" father.

Worked example: predicting a daughter's height

Now suppose a mother is 5'5" and a father is 6'0", and you want to estimate their daughter's adult height.

1. Convert to centimeters: 5'5" = 65 in × 2.54 = 165.10 cm; 6'0" = 72 in × 2.54 = 182.88 cm.
2. Apply the girl formula: (165.10 + 182.88 − 13) ÷ 2 = 334.98 ÷ 2 = 167.49 cm.
3. Convert back: 167.49 ÷ 2.54 ≈ 65.9 in, which rounds to 66 in = 5'6".
4. Add the range: 167.49 ± 8.5 cm = 158.99 to 175.99 cm, or about 5'3" to 5'9".

The daughter's most likely adult height is about 5'6", with a likely range of roughly 5'3" to 5'9". She lands taller than her mother because the father's height pulls the average up more than the girl adjustment (−6.5 cm) pulls it down.

Predicted height by parent heights

These tables apply the mid-parental formula to common parent-height combinations - mother's height down the left, father's height across the top - and show the most-likely adult height for a son and a daughter. Every value is computed with the formula above and rounded to the nearest inch, so they match what the calculator reports. Remember each figure carries a likely range of about ±3.3 inches.

Predicted son's adult height

Predicted daughter's adult height

Reading across a row shows how much a taller father shifts the estimate; reading down a column shows the mother's effect. Because the two parents contribute equally, a 2-inch change in either one moves the prediction by about an inch.

How to use this height calculator

You need three things to get a result - the child's sex and both parents' heights. Optional current-height fields add context but do not change the estimate.

1. Pick your units: use the toggle for US units (feet and inches) or metric (centimeters). Set this first so the labels match what you type.
2. Choose the child's sex: boy or girl. This decides whether the formula adds or subtracts the 6.5 cm adjustment.
3. Enter both parents' heights: the mother's and the father's. The estimate is only as good as these two numbers, so measure rather than guess where you can.
4. Optionally add the child's current age and height: the tool will show that measurement next to the prediction. It does not recalculate the estimate from it - the mid-parental figure comes from the parents alone.
5. Read the result: the calculator shows the most-likely adult height, the ±8.5 cm range, and how it compares with the average US adult.

What the plus-or-minus range means

The single number the formula produces is the center of a distribution, not a guarantee. The ±8.5 cm (±3.3 in) band is roughly a 95% range: about 19 in 20 children with those parents would be expected to land inside it, and the child is most likely near the middle. That is a spread of about 6.6 inches from the low end to the high end, which is genuinely wide - a reminder that two siblings with the same parents can differ noticeably in adult height. When a tool quotes a single height to the inch with no range, it is overstating how precise this method can be.

Growth charts and percentiles

Pediatricians do not use the mid-parental formula to track growth - they use growth charts. On a CDC or WHO chart, a child's height is plotted against age on a set of curves labeled by percentile, from the 3rd up to the 97th. A child on the 50th-percentile line is exactly average for their age and sex; one on the 90th is taller than 90% of peers; one on the 10th is shorter than 90% of them. Being at a low or high percentile is not itself a problem - what clinicians watch is whether a child tracks steadily along their own curve. Most children settle onto a percentile by about age 2 or 3 and follow it fairly closely, which is why a child who is tall or short for their age today often stays near that percentile. A curve that suddenly crosses several percentile lines, up or down, is the pattern that prompts a closer look.

The "2 x height at age 2" rule of thumb

You may have heard that you can double a child's height at age 2 to estimate their adult height. It is a folk rule, not a clinical method, and it is only a loose approximation. By that rule, a toddler who measures 34 inches at their second birthday would be estimated at about 68 inches, or 5'8"; one at 36 inches would come out around 6'0". The rule tends to run a little closer for boys, since girls are relatively further along their growth curve at age 2. It is a fun party trick, but the mid-parental formula uses more information - both parents' heights - and a pediatrician's growth-chart tracking beats both.

What changes a child's final height

Genetics sets the likely range, but several factors decide where in that range - or occasionally outside it - a child lands:

• Nutrition: steady, balanced nutrition through childhood lets a child reach more of their genetic potential; sustained undernutrition is the classic reason a child falls short of it.
• Puberty timing: the growth spurt and the eventual closing of the growth plates happen during puberty, so children who develop earlier or later finish growing at different ages - which shifts both the timing and, sometimes, the final height.
• General health: some chronic conditions and certain long-term medications can influence growth, which is one reason pediatricians monitor height over time.
• Sleep and overall well-being: growth is a whole-body process, and a healthy, well-rested childhood supports it - though no single habit "adds inches" beyond a child's genetic range.

None of these are captured by the parents' heights alone, which is precisely why the formula reports a range rather than one exact number.

How much of height is genetic?

Height is one of the most heritable human traits. According to NIH's MedlinePlus, scientists estimate that about 80% of a person's height is determined by the DNA they inherit, with the rest shaped by environment - chiefly nutrition and health during the growing years. The genetics are complex: hundreds of gene variants each contribute a little, and they combine unpredictably, which is why a child's height is a range centered on the parents rather than a fixed copy of them. It is also why two children of the same parents can differ, and why a child can be taller or shorter than both.

Can a child be taller than both parents?

Absolutely, and it is common. Because the estimate is a most-likely value inside a wide band, real outcomes scatter above and below it. A few scenarios show why:

• Favorable genetic mix: each parent carries many height-related variants, and a child can inherit a taller-than-average combination that neither parent fully expresses.
• Better childhood nutrition: across generations, improved nutrition has pushed average heights up, so children sometimes out-grow parents raised in leaner circumstances.
• Regression toward the mean: children of two very tall or two very short parents tend to be pulled slightly toward the population average - so very tall parents may have a child a bit shorter than themselves, and very short parents a child a bit taller.

When parents talk to a pediatrician about height

This calculator is for curiosity, not clinical decisions. In practice, height is one of the things pediatricians measure at every routine checkup, plotting it on a growth chart and watching the trend across visits. The patterns that usually get a closer look are growth that flattens out over time, a child who is much shorter or taller than the mid-parental estimate would suggest, or a height curve that crosses several percentile lines. A pediatrician can place a child's height in the full context of their growth history, weight, and development - which a one-off formula cannot do.

Who this calculator is for

• Curious parents who want a reasonable estimate of how tall a child may become.
• Expecting parents imagining a future child's height from their own heights.
• Teens and young adults wondering where they might finish, based on their parents.
• Anyone comparing a mid-parental estimate with a child's current growth for context.

It is not a diagnostic tool. It will not work well without both biological parents' heights, and it should not be used to judge whether a child's growth is healthy - that is what growth charts and a pediatrician are for.

Limitations and assumptions

• It uses only the two parents' heights - it ignores nutrition, puberty timing, health, and every non-parental genetic factor.
• It gives a range, not a date - it says nothing about when a child will reach their adult height.
• The ±8.5 cm band is wide on purpose; a child can reasonably land anywhere in it, and occasionally outside it.
• It assumes both biological parents' heights are known and reasonably accurate; estimates or unknown heights reduce reliability.
• It is not a medical assessment and does not replace growth-chart tracking by a clinician.

Key terms explained

• Mid-parental height: the estimate of a child's adult height built from the average of the parents' heights, adjusted for the child's sex.
• Tanner method: the common name for this mid-parental formula, after the growth researcher James Tanner.
• Target range: the ±8.5 cm (±3.3 in) band around the mid-parental estimate within which most children finish.
• Growth chart: a clinical chart plotting height (or weight) against age on percentile curves, used to track a child over time.
• Percentile: a child's rank among peers of the same age and sex - the 50th percentile is average, the 90th is taller than 90% of them.
• Heritability: the share of variation in a trait explained by genes; for height it is roughly 80%.

Sources

• Centers for Disease Control and Prevention (CDC) - Clinical growth charts (height-for-age percentiles).
• NIH National Library of Medicine, MedlinePlus Genetics - Is height determined by genetics? (about 80% heritability).
• World Health Organization (WHO) - Child growth standards.