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Baby Weight Percentile Calculator (0-24 Months) — WHO
A baby's weight percentile shows what percentage of babies of the same age and sex weigh less than yours, based on WHO Child Growth Standards from birth to 24 months. Between the 3rd and 97th percentile weight is considered normal as long as the baby follows their own curve. If the baby was born before 37 weeks, the percentile is computed at corrected age (chronological age minus the weeks short of 40), because comparing by chronological age would place them artificially low.
Is your baby's weight on track? Weight, length and head circumference percentiles on WHO charts from birth to 24 months, with corrected age for premature babies. Instant, free.
Medically reviewed by Dr. Ivan IbáñezNº Col. 17/05487Mar 8, 2026
CalcVita. (2026). Baby Weight Percentile Calculator (0-24 Months) — WHO. CalcVita. Retrieved October 16, 2026, from https://calcvita.com/en/calculators/child-weight-percentile
Suggested article
When Should I Worry About My Baby's Weight?
Learn to tell the difference between normal weight fluctuations and genuine warning signs, understand what percentiles really mean, and know when to call your pediatrician.
Read the full article →Key takeaways
- Compares weight, length and head circumference against WHO standards from 0 to 24 months.
- The 3rd–97th percentile range is normal; what matters is staying on the same track.
- For premature babies (< 37 weeks) the percentile uses corrected age until age 2.
- A drop of two percentile lines in a short time warrants a visit to the paediatrician.
Weight percentile guide
Weight is a sensitive indicator of current nutrition. Sudden shifts in weight percentile are often the first sign of a health or feeding issue.
How it works
WHO growth curves are based on data from 8,440 children across 6 countries (Brazil, Ghana, India, Norway, Oman, and the USA). They represent optimal growth under ideal conditions: breastfeeding, no household smoking, and adequate healthcare.
Interpreting the percentile
| Percentile range | Meaning |
|---|---|
| < P3 | Requires paediatric evaluation to rule out malnutrition or other causes. |
| P3 – P15 | Low weight, but may be normal if the curve is stable and family genetics support it. |
| P15 – P85 | Normal range. Most healthy children fall here. |
| P85 – P97 | High weight, but may be normal in genetically larger children. Monitor the trend. |
| > P97 | Requires paediatric evaluation to rule out overweight or obesity. |
When to worry
A single percentile reading is rarely cause for alarm. The following patterns do warrant medical consultation:
- Sudden drop of 2 or more major percentile lines in a short period.
- Percentile persistently below 3 or above 97 with no family history to explain it.
- Marked discordance between weight percentile and height percentile (e.g. weight at P10 and height at P90).
Practical tips
- Weigh the child at the same time of day, with the same clothing (or undressed), and on the same scale for comparable data.
- The trend matters more than a single number. Record weight periodically and observe the curve over months.
- Do not restrict a child’s diet without professional guidance, even if the percentile seems high.
Sources
- WHO Multicentre Growth Reference Study Group. WHO Child Growth Standards: Length/height-for-age, weight-for-age, weight-for-length, weight-for-height and body mass index-for-age. Geneva: World Health Organization; 2006.
- WHO Multicentre Growth Reference Study Group. WHO Child Growth Standards: Head circumference-for-age, arm circumference-for-age, triceps skinfold-for-age and subscapular skinfold-for-age. Geneva: World Health Organization; 2007.
- Engle WA; American Academy of Pediatrics Committee on Fetus and Newborn. “Age terminology during the perinatal period.” Pediatrics. 2004;114(5):1362-1364. PMID: 15520122.
- Bright Futures/American Academy of Pediatrics. Recommendations for Preventive Pediatric Health Care (periodicity schedule).
WHO head circumference chart by month (0-24 months)
Head circumference percentiles in centimetres from the WHO Child Growth Standards (2006), computed from the same LMS tables the calculator uses. The 3rd to 97th percentile range is normal; what matters is that the baby follows their own curve. To measure, run the tape just above the eyebrows and over the most prominent part of the back of the head.
Boys
| Age (months) | P3 | P15 | P50 | P85 | P97 |
|---|---|---|---|---|---|
| 0 | 32.1 | 33.1 | 34.5 | 35.8 | 36.9 |
| 1 | 35.1 | 36.1 | 37.3 | 38.5 | 39.5 |
| 2 | 36.9 | 37.9 | 39.1 | 40.3 | 41.3 |
| 3 | 38.3 | 39.3 | 40.5 | 41.7 | 42.7 |
| 4 | 39.4 | 40.4 | 41.6 | 42.9 | 43.9 |
| 5 | 40.3 | 41.3 | 42.6 | 43.8 | 44.8 |
| 6 | 41.0 | 42.1 | 43.3 | 44.6 | 45.6 |
| 7 | 41.7 | 42.7 | 44.0 | 45.3 | 46.3 |
| 8 | 42.2 | 43.2 | 44.5 | 45.8 | 46.9 |
| 9 | 42.6 | 43.7 | 45.0 | 46.3 | 47.4 |
| 10 | 43.0 | 44.1 | 45.4 | 46.7 | 47.8 |
| 11 | 43.4 | 44.4 | 45.8 | 47.1 | 48.2 |
| 12 | 43.6 | 44.7 | 46.1 | 47.4 | 48.5 |
| 15 | 44.3 | 45.5 | 46.8 | 48.2 | 49.3 |
| 18 | 44.9 | 46.0 | 47.4 | 48.7 | 49.9 |
| 21 | 45.3 | 46.4 | 47.8 | 49.2 | 50.4 |
| 24 | 45.7 | 46.8 | 48.3 | 49.7 | 50.8 |
Girls
| Age (months) | P3 | P15 | P50 | P85 | P97 |
|---|---|---|---|---|---|
| 0 | 31.7 | 32.7 | 33.9 | 35.1 | 36.1 |
| 1 | 34.3 | 35.3 | 36.5 | 37.8 | 38.8 |
| 2 | 36.0 | 37.0 | 38.3 | 39.5 | 40.5 |
| 3 | 37.2 | 38.2 | 39.5 | 40.8 | 41.9 |
| 4 | 38.2 | 39.3 | 40.6 | 41.9 | 43.0 |
| 5 | 39.0 | 40.1 | 41.5 | 42.8 | 43.9 |
| 6 | 39.7 | 40.8 | 42.2 | 43.5 | 44.6 |
| 7 | 40.4 | 41.5 | 42.8 | 44.2 | 45.3 |
| 8 | 40.9 | 42.0 | 43.4 | 44.7 | 45.9 |
| 9 | 41.3 | 42.4 | 43.8 | 45.2 | 46.3 |
| 10 | 41.7 | 42.8 | 44.2 | 45.6 | 46.8 |
| 11 | 42.0 | 43.2 | 44.6 | 46.0 | 47.1 |
| 12 | 42.3 | 43.5 | 44.9 | 46.3 | 47.5 |
| 15 | 43.1 | 44.2 | 45.7 | 47.1 | 48.2 |
| 18 | 43.6 | 44.8 | 46.2 | 47.7 | 48.8 |
| 21 | 44.1 | 45.3 | 46.7 | 48.2 | 49.4 |
| 24 | 44.6 | 45.7 | 47.2 | 48.6 | 49.8 |
The WHO publishes head circumference up to 5 years; enter the measurement above to get your baby’s exact percentile at their age in days.
Frequently asked questions
- What is a normal weight percentile?
- Generally, the range between the 3rd and 97th percentile is considered normal. The most important thing is not the number, but that the child steadily maintains their own growth channel.
- What does it mean to be in the 75th, 50th, or 25th percentile?
- It means your child weighs more than 75%, 50%, or 25% of children of the same age and sex. The 50th percentile is the median.
- What if my child is underweight?
- A percentile below 3 requires pediatric evaluation. However, some children are naturally thin due to genetics (thin parents) and are healthy if their growth curve is stable.
- What is a normal weight percentile for a baby?
- Any percentile between the 3rd and 97th is considered within the normal range. Most healthy babies fall within this span, and the key factor is that the baby follows their own growth curve consistently over time.
- Should I worry if my baby is in a low percentile?
- Not necessarily. Consistency matters more than the absolute number: a baby who stays steadily at the 10th percentile is usually healthy. Concern is warranted if there is a sudden drop of two or more percentile lines in a short period.
- How often should I check my baby's weight percentile?
- The American Academy of Pediatrics (Bright Futures) schedule sets well-child visits at birth, at 3-5 days and at 1, 2, 4, 6, 9, 12, 15, 18, 24 and 30 months, then once a year. Each country has its own schedule, so follow the one your paediatrician gives you.
- What is the difference between WHO and CDC growth charts?
- WHO charts are based on breastfed children from 6 countries and represent optimal growth from 0 to 5 years. CDC charts describe how American children grow from 2 to 20 years. WHO is the internationally recommended standard for children under 5.
- Can premature babies use the same percentile charts?
- Premature babies require the use of corrected age (chronological age minus weeks of prematurity) at least until age 2. Without correction, their percentiles will appear artificially low and will not reflect their actual growth. This calculator applies it automatically when you enter the weeks of gestation at birth.
- What is a normal head circumference for a baby?
- According to the WHO, the median (P50) for boys is 34.5 cm at birth, 40.5 cm at 3 months, 43.3 cm at 6 months, 46.1 cm at 1 year and 48.3 cm at 2 years; for girls 33.9 / 39.5 / 42.2 / 44.9 / 47.2 cm. The 3rd to 97th percentile range, about ±2.4 cm around the median, is considered normal. The full month-by-month chart is below and the calculator gives the exact percentile.
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