The simple answer is: the WHO Z-Score in the Poshan Calculator is a single number that shows where your child’s growth stands compared to healthy children of the same age and sex worldwide. If the number is between -2 and +2, growth is on track. If it falls below -2, your child may be stunted, wasted, or underweight.
Every month, Anganwadi workers weigh and measure lakhs of children. But a raw number like “8.5 kg” means little on its own — is it healthy for a two-year-old girl, or too low? The WHO Z-Score Poshan calculation compares your child’s measurements against the World Health Organization (WHO) Child Growth Standards, the same global reference used by doctors and health programmes in over 100 countries.
👉 Check your child’s growth right now with the free Poshan Calculator — enter age, sex, weight, and height for instant WHO z-scores, no download needed.
In this article, you will understand:
- What a z-score is and why doctors trust it more than raw weight or height
- The exact cut-offs that classify a child as Normal, MAM, SAM, or overweight
- The difference between stunting, wasting, and underweight — and why each needs a different response
- How to read your result and what to do next
What Exactly Is a Z-Score in Child Growth?
A z-score says “how far is this measurement from the healthy average?” The average comes from the WHO Multicentre Growth Reference Study, which measured over 8,000 healthy, well-fed children from six countries — Brazil, Ghana, India, Norway, Oman, and the United States. Their growth is now the global yardstick.
- Z-score of 0: exactly at the middle (median) of healthy children.
- Between -1 and +1: a little above or below the middle — perfectly normal.
- Below -2: low enough to be a concern — malnutrition classifications begin here.
- Above +2: high enough to watch for overweight or obesity.
Key takeaway: A z-score is not a mark out of 100 — it is a distance from the healthy middle, and the important boundary is -2.
Why the WHO 2006 Growth Standards Are the Global Reference
Before 2006, different countries used different charts, so classifications varied across borders. The WHO 2006 Child Growth Standards describe how children should grow when their needs are met. Indian children were part of the reference study, so the standards are valid for Indian families, and Poshan Tracker plots every child’s measurements on these same curves. Details are in this open-access nutrition study.
How to Read the WHO Z-Score Poshan Result on Your Screen
The calculator shows three z-scores — height-for-age, weight-for-age, and weight-for-height. Read them step by step:
- Enter the basics correctly: date of birth (for exact age in months), sex, and whether the child is measured lying down (under 2 years) or standing up (2 years and older).
- Add the measurements: weight in kilograms and length/height in centimetres, taken in the morning with light clothing.
- Press calculate and find the three z-scores on the screen.
- Check each number against -2 and +2. Anything between -2 and +2 is normal; anything below -2 needs attention.
- Read the label — Normal, MAM, SAM, or overweight — next to each score.
Remember: the calculator is a screening aid, not a diagnosis.
Stunting Explained: Height-for-Age Below -2
Stunting means a child is too short for their age (height-for-age below -2). It signals chronic, long-term undernutrition — repeated illness or poor diet over many months, often starting in the first 1,000 days of life. Between -3 and -2 is moderate stunting; below -3 is severe. Stunting cannot be reversed quickly, but it can be prevented with good nutrition during pregnancy and the first two years. Talk to your Anganwadi worker about supplementary nutrition and feeding counselling.
Wasting Explained: Weight-for-Height Below -2
Wasting means a child is too thin for their height (weight-for-height below -2). It signals acute, recent undernutrition — often from a recent illness like diarrhoea or a sudden drop in food intake. Between -3 and -2 is MAM (Moderately Acutely Malnourished); below -3 is SAM (Severely Acutely Malnourished). Wasting is the most urgent indicator: a score below -3 needs immediate medical attention.
Key takeaway: Wasting tells you about what is happening right now, while stunting tells you about the past. Both matter.
Underweight Explained: Weight-for-Age Below -2
Underweight means a child weighs too little for their age (weight-for-age below -2) — a combined indicator, since a child can be underweight from stunting, wasting, or both. Between -3 and -2 is moderate; below -3 is severe. Underweight is useful for tracking community progress, but it cannot tell you why a child is underweight — always check the stunting and wasting scores separately.
What Do Normal, MAM, SAM, Overweight and Obesity Mean?
Here are the official WHO cut-offs the calculator uses:
| Z-score range | Classification | What it means |
|---|---|---|
| -2 to +2 | Normal | Growth on track; continue good feeding and care |
| -3 to -2 | MAM (moderate) | Extra food, counselling, and monthly follow-up needed |
| Below -3 | SAM (severe) | Urgent medical care and therapeutic feeding needed |
| Above +2 | Overweight | Review diet and active play; consult a doctor |
| Above +3 | Obesity | Medical guidance on diet and lifestyle needed |
👉 Key takeaway: Memorise two numbers — below -2 means act, above +2 means watch.
Why Boys and Girls Have Separate Growth Charts
Boys and girls grow at slightly different rates. Using one chart for both would wrongly flag many healthy girls as underweight and miss some undernourished boys. The WHO standards have separate tables for boys and girls, and the calculator asks for sex so it picks the right one — always double-check, as a wrong choice is a common cause of confusing results.
Age Bands Matter: How Standards Change as Your Child Grows
The WHO standards are month-by-month — expected weight and height change every month, fastest in the first year. Children under 2 are measured lying down (length); children 2 and older standing (height). Enter the exact date of birth, not an approximate age — “2 years” instead of “23 months” can shift the score noticeably.
👉 Bookmark the Poshan Calculator and re-check monthly to follow your child’s growth trend.
Common Mistakes That Give Wrong Z-Scores
- Wrong age: use the exact date of birth, not a rounded age.
- Wrong sex selected: verify boy/girl before calculating.
- Heavy clothing or shoes: weigh in light clothing, measure barefoot.
- Length vs height mix-up: under-2s lying down, over-2s standing up.
- Faulty equipment: Anganwadi centres use calibrated scales and stadiometers — home tools can mislead.
If a surprising result persists after careful re-measurement, treat it as a genuine signal to seek help.
What to Do After You Get the Result
- All scores normal: continue breastfeeding, timely complementary feeding, and regular monitoring.
- -3 to -2 (MAM/moderate): visit your Anganwadi centre for supplementary nutrition and feeding counselling.
- Below -3 (SAM/severe): seek medical care promptly — therapeutic feeding may be needed.
- Above +2 (overweight): ask a doctor about balanced meals and more active play.
Important: this is a screening aid, not a medical diagnosis — only a health worker or doctor can confirm a diagnosis.
Limitations: What the Z-Score Cannot Tell You
- It describes the body, not the cause — it cannot say whether poor diet, illness, or another condition is responsible.
- One reading is a snapshot — the trend over months matters more.
- It misses other problems like anaemia or vitamin deficiencies, which need separate checks.
- Premature babies may need corrected-age charts — ask your doctor.
FAQs
What is a good z-score for a child?
Any z-score between -2 and +2 is normal and healthy; a score near 0 means your child is close to the global median.
What is the difference between MAM and SAM?
MAM (Moderately Acutely Malnourished) is a weight-for-height score between -3 and -2; SAM (Severely Acutely Malnourished) is below -3 and needs urgent medical care.
Can a child be stunted and wasted at the same time?
Yes — stunting reflects long-term undernutrition and wasting reflects recent undernutrition, so a child can have both and needs both medical care and long-term feeding support.
Do I need to download anything to check z-scores?
No. The Poshan Calculator works in your browser with no download, using the same WHO 2006 standards as Poshan Tracker.
How often should I check my child’s z-score?
Monthly for children under 2, and at least every three months for ages 2 to 5 — matching the Anganwadi growth-monitoring schedule.
Conclusion
The WHO z-score turns confusing numbers into clear answers: below -2 means act, below -3 means urgent care, and between -2 and +2 means growth is on track. Understanding stunting, wasting, underweight, and the MAM/SAM classifications lets you read any growth report with confidence — and act early, when help works best. Always confirm concerning results with your Anganwadi worker or doctor.
👉 Check your child’s WHO z-scores in under a minute with the free Poshan Calculator — no download, no sign-up, just answers.