Height Percentile Calculator – Where Your Child Stands on the CDC Growth Chart
A height on its own is just a number — the percentile says how it compares with children of the same age and sex.
Your child’s details
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Your child’s height percentile
Right at the CDC median — taller than about 50% of boys his age, and shorter than about 50%.
Between the 50th and 75th percentilesThe comparison, in full
Right in the middle of the chart
A 50th-percentile height is the exact middle of the CDC reference: half of boys this age measure taller, half measure shorter. It is a description of where your child stands today, not a grade — healthy children grow happily at every line on the chart. What pediatricians watch over time is the pattern: a child who tracks steadily along one percentile line is usually growing exactly as expected.
A snapshot, not a verdict: a single percentile describes one measurement on one day. Growth is a pattern over months and years — the same child measured after a growth spurt, or before one, can sit on a different line. The notes further down explain what movement between lines does and does not mean.
Your child on the growth curve
The shaded band is the typical range between the 3rd and 97th percentile on the CDC chart. The middle line is the median. The marker is your child — change any detail above and it moves. Underneath, the same chart at your child’s exact age, line by line.
| Percentile band | Height at 10 years 0 months (boys) | What it usually means |
|---|---|---|
| Below the 3rd | Under 126.5 cm | Shorter than about 97 of 100 children this age. Common with shorter parents; worth mentioning at the next checkup, especially if the line keeps drifting down. |
| 3rd to 10th | 126.5 to 130.3 cm | The short end of the typical range. Many healthy children simply live on this line. |
| 10th to 25th | 130.3 to 134.2 cm | Below the middle of the chart, well inside the typical range. |
| 25th to 50th | 134.2 to 138.6 cm | Just under the median — an entirely ordinary place to be. |
| 50th to 75th | 138.6 to 143.1 cm | Just over the median — an entirely ordinary place to be. |
| 75th to 90th | 143.1 to 147.2 cm | Above the middle of the chart, well inside the typical range. |
| 90th to 97th | 147.2 to 151.3 cm | The tall end of the typical range. Many healthy children simply live on this line. |
| Above the 97th | Over 151.3 cm | Taller than about 97 of 100 children this age. Common with taller parents; worth mentioning at the next checkup if the line keeps climbing. |
A percentile is a position, not a target
The 50th percentile is simply the middle of the reference group — by definition, half of all healthy children sit below it. There is no prize for a higher line and no failure in a lower one. Children are built to different blueprints, and a child tracking the 8th percentile steadily is usually showing you their blueprint working exactly as intended.
The pattern matters more than the point
One measurement is a snapshot. What pediatricians read is the film: heights plotted over several visits, forming a channel. A steady channel at almost any level is reassuring. A channel that bends — crossing two or more major lines over time — is the signal doctors act on, and it can only be seen across visits, which is why the checkup measurements count.
CDC median heights at a glance
The 50th-percentile height for each age, from the same CDC table this calculator uses. Half of children measure above these numbers and half below — they are midpoints, not goals.
| Age | Boys — median height | Girls — median height |
|---|---|---|
| 2 years | 86.5 cm (2 ft 10.1 in) | 85.0 cm (2 ft 9.5 in) |
| 3 years | 95.0 cm (3 ft 1.4 in) | 93.9 cm (3 ft 1.0 in) |
| 5 years | 108.9 cm (3 ft 6.9 in) | 107.7 cm (3 ft 6.4 in) |
| 8 years | 127.9 cm (4 ft 2.4 in) | 127.6 cm (4 ft 2.2 in) |
| 10 years | 138.6 cm (4 ft 6.6 in) | 138.0 cm (4 ft 6.3 in) |
| 12 years | 149.1 cm (4 ft 10.7 in) | 151.2 cm (4 ft 11.5 in) |
| 15 years | 169.9 cm (5 ft 6.9 in) | 161.9 cm (5 ft 3.7 in) |
| 18 years | 176.2 cm (5 ft 9.4 in) | 163.1 cm (5 ft 4.2 in) |
| 20 years | 176.8 cm (5 ft 9.6 in) | 163.3 cm (5 ft 4.3 in) |
Keep exploring
A height on its own is just a number. What parents and pediatricians actually want to know is how that height compares with thousands of other children of the same age and sex — and that comparison is the percentile. This calculator places your child’s height on the official CDC stature-for-age growth charts for ages 2 to 20, using the same LMS method the CDC publishes, and returns the exact percentile and z-score in centimetres or feet and inches.
Key takeaways
- The shaded band is the typical range between the 3rd and 97th percentile on the CDC chart.
- Half of children measure above these numbers and half below — they are midpoints, not goals.
- Shoes off, heels, back and head against a flat wall, eyes looking straight ahead.
Contents
How to get a percentile you can trust, in three steps
Measure like a clinic
Shoes off, heels, back and head against a flat wall, eyes looking straight ahead. Lay a hardback book flat on the head, mark the wall at its underside, and measure the mark with a tape. Morning and evening readings can differ by about a centimetre, so compare like with like.
Give the exact age
Growth charts run on months, not birthdays. A tall-for-6 child and a tall-for-6-years-11-months child are being compared with different groups. Use years plus months, or the date of birth, which works the age out to the day.
Read the position, then track it
Note today’s percentile, then plot the next measurement a few months later. Staying on the same line is the expected, healthy pattern. Bring the series to checkups — your pediatrician reads the trend the same way, with your child’s health and family heights alongside.
The method, and every assumption in the open
The default example, worked end to end
Take a boy who is exactly 10 years old — 120.0 months. Interpolating the CDC table at that age gives L = 0.5026, M = 138.62 cm (the median height) and S = 0.0476. Enter his height as exactly the median, 138.62 cm: the ratio height / M is 1, so z = ((1)^0.5026 − 1) / (0.5026 × 0.0476) = 0.00, and the normal curve turns a z-score of 0 into the 50.0th percentile. The same boy at 147.2 cm: the ratio is 147.2 / 138.62 = 1.0619, z comes out at 1.28, and the percentile is the 90th — which is exactly where the CDC’s printed 90th-percentile line sits for this age. Two anchor points, both landing on the chart’s own lines.
Why a formula at all — why not just rank children?
Heights at any age spread out in a slightly lopsided bell curve, and the lopsidedness changes as children grow. The LMS method captures each age with three numbers: M, the median; S, the spread around it; and L, a power that straightens the skew so the ordinary normal curve can be used. With those three, any height converts to a z-score — a position in standard-deviation units — and any z-score converts to a percentile. It is the method the CDC itself publishes for turning its survey measurements into the smooth curves on the growth chart, and it means this page’s numbers are the chart’s numbers, not an approximation of them.
Every assumption, printed
- The dataset: CDC stature-for-age LMS values from the CDC’s official data file (2000 growth charts, CDC / NCHS), 218 ages per sex from 24 to 240 months. The file was cross-checked against an archived copy of the same CDC file — identical in every cell — and the LMS maths was verified against the CDC’s own printed 3rd, 50th and 97th percentile columns at 42 age and sex points, matching to the last printed decimal.
- Interpolation: the CDC publishes rows at half-month steps. For an age between rows, L, M and S are interpolated linearly to the exact age in months — the standard approach for growth-chart software — and the z-score is computed from the interpolated values.
- Age from a birthdate: age in months = days since birth ÷ 30.4375 (the average month, 365.2425 ÷ 12), using today’s date. Years-and-months entry is summed exactly as given.
- Rounding: the percentile is shown to one decimal place and the z-score to two. Results beyond the chart’s readable edge are shown as below 0.1 or above 99.9 rather than as false-precision decimals.
- Units: 1 inch = 2.54 cm exactly. All maths runs in centimetres; the feet-and-inches figure is the converted result.
- The reference group: US children measured in national surveys between 1963 and 1994, the basis of the 2000 CDC charts. A percentile compares your child with that group; it is a reference, not a standard children are supposed to meet, and it says nothing by itself about nutrition or health.
- Range: the stature charts cover ages 2 to 20 years. Under 2, length is measured lying down and read on infant charts instead — a different chart for a different measurement.
Four ways a home percentile can mislead
Measurement first: shoes, a thick hairstyle, slouching, or a carpeted floor can each add or hide a centimetre, and a centimetre is several percentile points in a young child — the percentile may be reporting your tape measure, not your child. Timing second: a reading taken the week before a growth spurt and one taken the week after describe the same healthy child at different lines. Comparison third: siblings are not reference points for each other — different children inherit different mixes and mature on different clocks. And puberty fourth: early developers surge up the chart while late developers slide down it, sometimes for two years, before everyone lands where their genetics intended. All four are reasons pediatricians read growth as a series, and why this page keeps saying: plot the pattern, not just the point.
Going deeper
The curves on a CDC growth chart are not targets drawn by a committee — they are measurements. Between 1963 and 1994, US national health surveys (the National Health Examination Surveys and the NHANES programme) measured tens of thousands of children under standardised conditions. In 2000 the CDC and the National Center for Health Statistics published those measurements as the growth charts used in American clinics ever since. Statisticians smoothed the raw scatter into curves with the LMS method, which is why every percentile line bends the same organic way real growth does — fast in the toddler years, steady through middle childhood, surging at puberty, flattening by the late teens. Two consequences follow. The charts are a reference: they describe how US children of that era actually grew, including children of every build and background, so falling anywhere inside the band is statistically ordinary. And they start at age 2 for stature because below that age children are measured lying down — recumbent length, on separate infant charts — since a standing height cannot be taken reliably on a one-year-old. The World Health Organization publishes its own charts for the under-5s from an international cohort of breastfed children; American pediatricians generally use WHO charts under age 2 and CDC charts from 2 to 20, which is exactly the range this calculator covers.
Every few months a parent worries that their child has “dropped to” the 20th percentile, as if the chart were an exam. It is worth dismantling that idea properly. The median is a midpoint, not a standard of health: in the reference group itself, exactly half the children are below it, and they were measured precisely because they were ordinary, healthy kids. A child’s line is set mostly by inheritance — pediatricians estimate a child’s genetic target from the parents’ heights (the mid-parental height) and expect the child’s channel to sit near it, which is why the children of two short parents tracking the 6th percentile are usually a picture of health, and the child of two tall parents drifting from the 90th to the 55th may be the one worth a second look. What clinicians actually track, visit to visit, is growth velocity — school-age children typically add about 5 to 6 cm a year between age 4 and puberty — and whether the plotted points keep their channel while that velocity holds. Position tells you where a child stands among peers today; velocity and channel tell you whether growth itself is proceeding. The percentile this page gives you is the first of those, and it earns its keep when you collect it over time.
Frequently asked questions
What does a height percentile mean?
A height percentile says how your child’s height compares with the reference group of children the CDC measured — same age, same sex. A child at the 60th percentile is taller than about 60 out of every 100 children in that group, and shorter than about 40. The 50th percentile is the median: exactly in the middle. A percentile is a position, not a score — it does not say your child is growing well or badly, only where this one measurement falls in the spread of healthy children.
How is the height percentile calculated?
With the CDC’s LMS method. For every age and sex, the CDC publishes three numbers — L (the skew of the height distribution), M (the median height) and S (the spread). Your child’s height is turned into a z-score with z = ((height / M)^L − 1) / (L × S), and the standard normal curve converts that z-score into a percentile. This page uses the CDC’s official stature-for-age LMS table and interpolates L, M and S to your child’s exact age in months, the same approach growth-chart software in clinics uses.
What is a normal height percentile for a child?
Anywhere between the 3rd and the 97th percentile is the typical range — by construction it holds about 94 of every 100 children. There is no single normal line: a healthy child can track along the 5th percentile for years, and another along the 95th. Pediatricians care less about which line a child is on than whether they keep growing along it, because a steady channel usually means growth is on track for that child’s own genetic pattern.
Should I worry if my child is below the 3rd percentile or above the 97th?
Not automatically. About 3 in 100 perfectly healthy children fall below the 3rd percentile and 3 in 100 above the 97th — the lines have to cut the reference group somewhere. Parental height explains a great deal: shorter parents usually have shorter children. What does deserve a conversation with your pediatrician is a child who keeps crossing percentile lines downward over successive visits, grows much more slowly than before, or seems unwell in other ways. A single measurement outside the band is a prompt to keep watching, not a diagnosis.
How often should I measure my child’s height?
At routine checkups, your pediatrician plots height on the growth chart — typically once or twice a year for school-age children, and more often for toddlers. At home, measuring every few months is plenty; height changes too slowly for weekly numbers to mean anything, and small measurement differences (posture, hair, time of day — children can measure about 1 cm taller in the morning) can look like movement that is not really there. Use the same flat wall, bare feet and the same time of day for readings you compare.
Why did my child’s percentile change since last time?
Percentiles move for ordinary reasons. Children grow in spurts, and a measurement taken just before a spurt sits lower than one taken just after. Puberty timing shifts things too: early developers climb lines for a while, late developers dip and then catch up. Measurement noise plays a part — a centimetre here or there can shift a young child’s percentile by several points. Doctors look at the pattern across several visits, and the flag they watch for is a sustained crossing of two or more major percentile lines, not a single wobble.
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→This calculator places a height on the CDC stature-for-age growth charts (ages 2 to 20) for education and information. It is not medical advice and cannot diagnose a growth disorder or any other condition. A percentile describes one measurement against a reference group; growth is judged on the pattern across several measurements, together with growth velocity, parental heights, puberty timing and overall health — all things a calculator cannot see. Children under 2 are measured lying down and read on infant length-for-age charts, so this page does not cover them. If your child’s growth seems to slow, their percentile keeps crossing lines, or you are worried for any reason, talk to your pediatrician, who can measure accurately and look at the full picture.
One measurement, placed fairly — the exact CDC percentile, with the method in the open.
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