Weight
Undress the child or leave only light clothing (consistent between weighings — same with or without diaper). Place on the scale when still. Most accurate: before a feed, around the same time of day as the previous measurement.
Baby Growth Percentile Calculator — WHO
Enter your child's age, sex, and measurements — the calculator shows where they sit compared with WHO growth standards for healthy children (0–5 years). Correction for premature babies built in.
verified Last updated: May 2026 · WHO Standards 2006
Enter at least one measurement and click Calculate.
What WHO growth percentiles tell you
The WHO Child Growth Standards describe how a healthy baby grows under optimal conditions — breastfed, regularly followed up, free of chronic illness. The data come from six countries across different climates and ethnic backgrounds, which makes them globally applicable.
A percentile shows where your child sits within that group. If your baby is at the 25th weight percentile, 25% of healthy babies the same age and sex are lighter and 75% are heavier. Most children sit between the 3rd and 97th percentile; around 5% of children naturally fall outside that range and can still be perfectly healthy.
It helps to know what a percentile isn't: it isn't a grade. A child at the 10th percentile isn't "behind" a child at the 90th — they're just two builds within the same range of health. What pediatricians watch is the trend: is the child following their own curve, or has it dropped or jumped sharply? A sustained downward trend across several visits, or a sudden shift of two or more percentile channels, is what prompts further evaluation.
The calculator uses the LMS method — the same one pediatricians around the world use. For premature babies, it applies corrected age: weeks of prematurity are subtracted from chronological age, so percentiles reflect the child's actual developmental age. The correction tapers off as the child grows and disappears between 18 and 36 months.
What each percentile means
Quick reference for interpreting the calculator's result:
| Percentile | What it means |
|---|---|
| Below 3rd | Lower than most children — worth talking to the pediatrician |
| 3rd–10th | Lower end of typical range |
| 10th–25th | Lower quarter of typical range |
| 25th–75th | Middle range — where most children sit |
| 75th–90th | Upper quarter of typical range |
| 90th–97th | Higher end of typical range |
| Above 97th | Higher than most children — worth talking to the pediatrician |
Example interpretation
A 10-month-old boy weighing 8.9 kg sits at around the 35th weight percentile. About 35% of healthy boys his age weigh less, and about 65% weigh more — well within the typical range for healthy children. If previous measurements show him following that curve, there's usually no cause for concern.
groupsWhat parents most often notice
Numbers are one thing — here's how parents actually talk about growth in real life:
- Pediatrician watches the curve, not the absolute number
- Always weighing on the home scale
- Smaller than peers at daycare
- Big for age — already outgrowing clothes
- Jump between measurements after a feeding change
- Sibling differences at the same age
- Eats less but energy is normal
- Chubby cheeks or "well-rounded baby"
If sleep is rough at the same time or a tooth is breaking through, those are usually the cause — not growth itself. Check wake windows or the tooth eruption timeline first.
How to measure correctly
Accuracy depends on how the measurements are taken. Quick guide for at-home measuring:
Length or height
Under 2 years — child lies flat on a level surface, head touching a fixed point, knees extended, soles pressed gently. Over 2 years — standing upright, heels at the wall, looking straight ahead.
Head circumference
Soft tailor's tape around the widest points of the forehead and the back of the head, just above the brows. Pull lightly so it sits flush but doesn't compress. Measure 2–3 times and take the average.
The most reliable measurement is at the pediatrician's office — at home, it's a guide between visits.
When to talk to the pediatrician
- A result below the 3rd or above the 97th percentile and you don't have a routine follow-up scheduled.
- The child has dropped or jumped 2+ percentile channels in a short period (e.g. 50th to 10th).
- You feel something is off regardless of the number — feeding has changed, energy is low, the child is settling less easily.
- There's a family history of hormonal or growth conditions, or the child takes medication that affects growth.
The calculator gives you one data point. A well-child visit weighs physical exam, feeding, motor and speech development, and family build — things a single number can't capture.
Methodology
The calculator uses the WHO Child Growth Standards (2006) — the official LMS coefficients for children 0–5 years. The algorithm is identical to the one in the KidyGrow app that parents use to track growth over time, so results on the web and in the app always match.
Data source: WHO Child Growth Standards, official LMS tables from who.int/tools/child-growth-standards.
Last reviewed: May 2026. The standards haven't changed since 2006 — the date marks when our implementation was last verified against the official tables.
About the tool: KidyGrow was built by a parent and software engineer who wanted a simpler way to understand pediatric growth charts between doctor visits. The goal isn't to replace the pediatrician but to give parents clearer visibility into their child's data.
help_outlineFAQ
What are WHO growth percentiles?
Percentiles show where your child sits compared with healthy children of the same age and sex. The 50th percentile is the median — half of children sit below and half above. The 25th percentile means about 25% of children of the same age and sex have a lower value, and about 75% have a higher one.
Percentiles on their own aren't a diagnosis — the trend over time and the pediatrician's exam matter more.
What range is considered typical?
WHO most often considers the range between the 3rd and 97th percentile typical for healthy children. Below the 3rd or above the 97th isn't automatically a problem, but it's a reason to check in with the pediatrician, especially if the trend is shifting fast.
What if my baby was born premature?
For babies born before 37 weeks gestation, corrected age is used: chronological age minus the weeks of prematurity. Turn on Born premature — pediatricians most often apply correction up to about 18 months for head circumference, 24 months for weight, and 36 months for length.
Can I measure my baby at home?
Weight: a digital baby scale works if the child holds still. Length (under 2 years) is measured lying flat; height (over 2 years) standing. Head circumference: a soft tape measure around the widest points of the forehead and back of the head.
The most reliable measurements come from the doctor's office — at home, they're a guide between visits.
Can a baby stay on the 10th percentile and still be healthy?
Yes, most often. A lower percentile on its own isn't a problem as long as the child tracks their own curve over time and develops as expected. Babies who are steadily at the 10th percentile from birth are often simply smaller-framed, especially if the parents are smaller too.
The reason to look closer is a sharp drop from a higher percentile or other signs: feeding has changed, slower development, lower energy.
What causes a low weight percentile?
The most common reasons: genetics (smaller parents usually have smaller children), prematurity (corrected age is used for premature babies), growth spurts (temporary swings of ±1 percentile channel) and insufficient intake (poor latch in breastfeeding, smaller feeds, picky eating in older babies).
A smaller share of children have a medical cause — allergies, intolerances, infections, hormonal issues, metabolic concerns. The pediatrician distinguishes benign causes from those that need further evaluation.
Should I worry about head circumference percentile?
Head circumference is the second most important growth indicator in the first 2 years because it reflects brain growth — that's why pediatricians measure it at every well-child visit. The typical range is the 3rd to the 97th percentile.
A sharp upward jump (more than 2 percentile channels in a few months) can suggest hydrocephalus and warrants evaluation. A sharp drop can indicate slowed brain growth. A stable lower or higher percentile without other symptoms is most often normal variation — you track the trend, not the single number.
Does this replace a pediatrician?
No. WHO percentiles are one data point — your pediatrician looks at physical exam, feeding, development, and family build. Use the tool between visits to get a sense of where your child sits, but intervention decisions happen with the doctor.
Sources
- WHO Child Growth Standards (0–5 years) — official source of LMS coefficients used in this calculator.
- WHO (2006). Child Growth Standards: Length/height-for-age, weight-for-age, weight-for-length, weight-for-height, BMI-for-age — methods document.
- American Academy of Pediatrics — well-child visit recommendations for growth monitoring.
Standards apply to healthy children born at term and to premature children after age correction. For children with chronic conditions or special medical needs, condition-specific reference curves apply — your pediatrician will use the right one.