Child Height Percentile Calculator
Find your child's height percentile on the official WHO growth reference using the LMS z-score method — the same math pediatricians use. Ages 0 to 19 years. Metric and imperial. 100% private: everything runs in your browser.
Calculate height percentile
Z-score: – · Reference: –
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Growth-channel tracker
Add measurements over time to see which growth channel (percentile curve) your child follows. A child who crosses channels — e.g. drops from the 60th to the 25th percentile — should be discussed with a pediatrician.
| Age | Height | Percentile | Z |
|---|
What the percentile means
A height percentile tells you how your child's height compares with the WHO reference population of the same age and sex. The 50th percentile is the median — half of children are taller, half are shorter. The 25th percentile means 25 out of 100 children are shorter (75 are taller). It is not a grade: a healthy child can sit at the 5th or the 95th percentile, as long as they stay on their channel.
The LMS z-score method (honest math)
This calculator does not guess from a coarse table. It uses the LMS method published by the World Health Organization:
z = ((height / M)L − 1) / (L × S)
For every age and sex, WHO publishes three parameters: L (skew), M (median), S (spread). In the WHO height references L = 1.0 at every age (verified against WHO's official data files), so the formula simplifies to z = (height / M − 1) / S. The z-score is converted to a percentile with the standard normal distribution. Fractional ages are handled by interpolating M and S — the same approach WHO's own software uses.
Three reference bands
| Age | Reference | Measured |
|---|---|---|
| 0–24 months | WHO Child Growth Standards (MGRS) | Recumbent length, daily values |
| 24–60 months | WHO Child Growth Standards (MGRS) | Standing height, daily values |
| 5–19 years | WHO Growth Reference 2007 | Standing height, monthly values |
At 24 months WHO switches from lying-down to standing measurement; the reference medians differ by 0.7 cm there — this calculator applies WHO's 0.7 cm adjustment automatically when the measurement method differs from the reference. At 60/61 months the MGRS and 2007 references join with a step of under 0.35 cm.
WHO vs CDC: which reference?
In the United States, clinicians typically use the CDC 2000 growth charts from age 2 to 20. This calculator uses the WHO references for all ages because the CDC's published LMS tables could not be retrieved (their data endpoint returned an access error during development), while the WHO parameters are published openly and verifiable. For most children the two references agree closely; if your pediatrician uses CDC charts, expect small differences after age 2 — the method (LMS z-score) is identical.
Growth channels and when to pay attention
Children tend to grow along a channel — a percentile curve they follow over time. The tracker above draws the z = −2, −1, 0, +1, +2 curves (roughly the 2nd, 16th, 50th, 84th and 98th percentiles). What matters most is not a single point, but the pattern:
- Staying on a channel — even the 5th or 95th — is usually normal.
- Crossing two or more channels (e.g. 75th → 25th) over months deserves a pediatrician's look, whatever the absolute percentile.
- Below the 3rd or above the 97th percentile (z beyond ±2) is outside the typical range — worth discussing, not a diagnosis by itself.
Reference medians (sample)
Median (50th percentile) heights from the WHO references used by this calculator. The engine holds daily values for 0–5 years and monthly values for 5–19 years.
| Age | Boys | Girls |
|---|---|---|
| Birth | 49.9 cm | 49.1 cm |
| 6 months | 67.6 cm | 65.7 cm |
| 12 months | 75.7 cm | 74.0 cm |
| 2 years | 87.8 cm | 86.4 cm |
| 5 years | 110.0 cm | 109.4 cm |
| 10 years | 137.8 cm | 138.6 cm |
| 15 years | 169.0 cm | 161.7 cm |
| 19 years | 176.5 cm | 163.2 cm |
Worked examples
Each example was computed by the engine on this page (LMS z-score, not table lookup).
Example 1 — 12-month-old boy, 78.5 cm
Reference (Band A): M = 75.7 cm, S = 0.0314. z = (78.5 / 75.7 − 1) / 0.0314 = 1.16 → 87.7th percentile. Taller than about 88 in 100 boys his age.
Example 2 — 3-year-old girl, 92.0 cm
Reference (Band B): M = 95.1 cm, S = 0.0401. z = (92.0 / 95.1 − 1) / 0.0401 = −0.80 → 21.2nd percentile. Shorter than average, well within the typical range (above the 3rd percentile).
Example 3 — 10-year-old boy, 130 cm
Reference (Band C, WHO 2007): M = 137.8 cm, S = 0.0463. z = −1.22 → 11.1th percentile. Below average; a single measurement here is not a concern by itself, but the channel over time matters.
Example 4 — 15-year-old girl, 155 cm
Reference: M = 161.7 cm, S = 0.0425. z = −0.97 → 16.6th percentile.
Example 5 — 6-month-old boy, 70 cm
Reference: M = 67.6 cm, S = 0.0317. z = 1.11 → 86.7th percentile.
Frequently asked questions
What percentile is considered normal for a child's height?
Any percentile between the 3rd and 97th is within the typical range — including the 5th or the 95th. What matters more than one number is the pattern: a child who steadily follows their own channel (say, the 20th percentile at every checkup) is usually growing normally.
How is the height percentile calculated?
With the LMS z-score method from the World Health Organization. For your child's exact age and sex, the calculator takes WHO's published L, M and S parameters and computes z = ((height/M)^L − 1)/(L×S) — with L = 1.0 in the WHO height references this is z = (height/M − 1)/S — then converts the z-score to a percentile. Example: a 12-month-old boy at 78.5 cm scores z = 1.16, which is the 87.7th percentile.
Should I use WHO or CDC growth charts?
Both use the same LMS math. WHO references describe how children should grow under good conditions and are the international standard; the CDC 2000 charts describe how US children did grow and are commonly used by US clinicians from age 2. This calculator uses WHO references for all ages (0–19 years) because the WHO parameters are openly published and verifiable. Expect only small differences versus CDC charts after age 2.
Why does the percentile change at 24 months?
WHO measures recumbent length (lying down) before 24 months and standing height from 24 months. Standing height averages 0.7 cm less than length, so the reference medians step by 0.7 cm at 24 months (87.8 vs 87.1 cm for boys). The calculator applies WHO's 0.7 cm adjustment automatically if the measurement method differs from the reference.
What does it mean to "cross growth channels"?
Growth channels are the percentile curves (e.g. the 25th, 50th, 75th). Children usually track along one channel. Dropping across two or more channels — for instance from the 60th to the 25th percentile over several months — is a stronger signal than any single measurement and is worth discussing with a pediatrician. The tracker above draws these channels and flags crossings automatically.
My child is below the 3rd percentile. Should I worry?
Not from one number alone — about 3 in 100 healthy children fall below the 3rd percentile by definition. What matters is context: has your child always been small (consistent channel, parents are short)? Or is this a new drop? Persistent measurements below the 3rd percentile, or a downward crossing of channels, are reasons to see a pediatrician — not a diagnosis.
Can this predict my child's adult height?
No — a height percentile is not an adult-height prediction. Adult height depends on genetics (parents' heights), puberty timing and health. For a mid-parental target-height estimate, see our height calculator (child adult-height predictor).
How accurate is the calculator for premature babies?
Use corrected age (age from the due date, not the birth date) until at least 24 months — most pediatricians correct to 24 months for height. Enter the corrected age in the calculator. Example: a baby born 2 months early who is 8 months old chronologically should be entered as 6 months.
Does it work in feet/inches?
Yes — switch the unit to inches. Conversions use 1 in = 2.54 cm exactly. Example: 34.3 in = 87.1 cm.
Is my child's data stored or sent anywhere?
No. Every calculation runs locally in your browser with JavaScript; nothing is uploaded, stored or tracked. The tracker keeps measurements only in the page's memory — they disappear when you close the tab.
What is a z-score in simple terms?
A z-score is the number of standard deviations from the median. z = 0 is exactly average (50th percentile); z = +1 is one standard deviation above (84th percentile); z = −1 is one below (16th percentile). z = ±2 marks the 2nd/98th percentiles — the usual "typical range" boundary.
Why is my percentile slightly different from my pediatrician's chart?
Small differences come from three places: (1) the reference (WHO here vs CDC at many US clinics), (2) exact-age interpolation — this calculator interpolates to the day, paper charts round to the month, and (3) the 0.7 cm length/height adjustment near age 2. Differences under 2–3 percentile points are normal method noise, not error.
Related tools
- Height calculator — adult & child height prediction (mid-parental target height)
- Head circumference percentile — WHO head-circumference-for-age (0–5 years)
- BMI percentile (child) — BMI-for-age percentile
- Child BMI calculator — BMI with interpretation
- Pediatric blood pressure — BP percentile by age, sex & height
Free tool by NRTechStudio