Baby Weight Percentile Calculator (WHO)
"The WHO weight-for-age tables for 0–24 months, with percentiles from the 3rd to the 97th for boys and girls, plus how to read your baby's number and what it actually means."
A weight percentile compares your baby’s weight with the WHO Child Growth Standards, a reference population of healthy breastfed children measured in six countries between 1997 and 2003.1 The number answers one question: heavier than what share of same-age, same-sex babies? If your pediatrician says “60th percentile,” this is where that figure comes from, and you can look it up yourself in about thirty seconds.
Below are the complete weight-for-age tables for boys and girls, birth to 24 months, at the 3rd, 10th, 25th, 50th, 75th, 90th, and 97th percentiles.2
How to use the tables
- Find your baby’s age in the left column, in months. Round to the nearest listed age.
- Find the measured weight on that row, in kilograms. If your scale reads pounds, divide by 2.205.
- Read the percentile at the top of the nearest column. That’s the number your pediatrician quotes.
Worked example. A 6-month-old girl weighs 7.3 kg. The 6-month row in the girls’ table shows 7.3 at the 50th percentile, the median. A 12-month-old boy at 11.8 kg lands on the 97th percentile in the boys’ table, the top edge of the typical band.
For a day-exact percentile, use the baby weight percentile calculator instead of the month-level tables.
Boys: WHO weight-for-age, 0–24 months (kg)
| Age | P3 | P10 | P25 | P50 | P75 | P90 | P97 |
|---|---|---|---|---|---|---|---|
| Birth | 2.5 | 2.8 | 3.0 | 3.3 | 3.7 | 4.0 | 4.3 |
| 1 month | 3.4 | 3.7 | 4.1 | 4.5 | 4.9 | 5.3 | 5.7 |
| 2 months | 4.4 | 4.7 | 5.1 | 5.6 | 6.1 | 6.5 | 7.0 |
| 3 months | 5.1 | 5.5 | 5.9 | 6.4 | 6.9 | 7.4 | 7.9 |
| 4 months | 5.6 | 6.1 | 6.5 | 7.0 | 7.6 | 8.1 | 8.6 |
| 5 months | 6.1 | 6.5 | 7.0 | 7.5 | 8.1 | 8.6 | 9.2 |
| 6 months | 6.4 | 6.9 | 7.4 | 7.9 | 8.5 | 9.1 | 9.7 |
| 9 months | 7.2 | 7.7 | 8.3 | 8.9 | 9.6 | 10.2 | 10.9 |
| 12 months | 7.8 | 8.4 | 9.0 | 9.6 | 10.4 | 11.1 | 11.8 |
| 18 months | 8.9 | 9.5 | 10.1 | 10.9 | 11.8 | 12.6 | 13.5 |
| 24 months | 9.8 | 10.5 | 11.2 | 12.1 | 13.1 | 14.1 | 15.1 |
Girls: WHO weight-for-age, 0–24 months (kg)
| Age | P3 | P10 | P25 | P50 | P75 | P90 | P97 |
|---|---|---|---|---|---|---|---|
| Birth | 2.4 | 2.7 | 2.9 | 3.2 | 3.6 | 3.9 | 4.2 |
| 1 month | 3.2 | 3.5 | 3.8 | 4.2 | 4.6 | 5.0 | 5.4 |
| 2 months | 4.0 | 4.3 | 4.7 | 5.1 | 5.6 | 6.1 | 6.5 |
| 3 months | 4.6 | 5.0 | 5.4 | 5.8 | 6.4 | 6.9 | 7.4 |
| 4 months | 5.1 | 5.5 | 5.9 | 6.4 | 7.0 | 7.5 | 8.1 |
| 5 months | 5.5 | 5.9 | 6.3 | 6.9 | 7.5 | 8.1 | 8.7 |
| 6 months | 5.8 | 6.3 | 6.7 | 7.3 | 7.9 | 8.5 | 9.2 |
| 9 months | 6.6 | 7.0 | 7.6 | 8.2 | 8.9 | 9.6 | 10.4 |
| 12 months | 7.1 | 7.7 | 8.2 | 8.9 | 9.7 | 10.5 | 11.3 |
| 18 months | 8.2 | 8.8 | 9.4 | 10.2 | 11.1 | 12.0 | 13.0 |
| 24 months | 9.2 | 9.8 | 10.6 | 11.5 | 12.5 | 13.5 | 14.6 |
What the number means
- The 50th percentile is the median, not a target. Above or below it is not better or worse.
- The 3rd to 97th band is the typical range: roughly 94% of healthy babies fall inside it.3
- Below the 3rd or above the 97th is a flag for closer attention, not a diagnosis.
- Percentile is a rank, not a percentage: the 90th percentile means heavier than 90% of healthy peers, not “90% of some ideal weight.”
Four caveats
- Age precision matters. The full data is day-by-day; these tables round to month-level reference ages.4 For an exact number, a charting tool that knows the day beats a table.
- Correct for prematurity. Babies born before 37 weeks are typically plotted by corrected age (age since the due date) until about age 2. Using uncorrected age understates their percentile.
- Match the sex. Boys and girls grow at different rates, so read only the table for your baby’s sex.
- Scales and timing add noise. Weights taken on different scales, or before versus after a feed, vary by a few hundred grams, enough to move a percentile or two. Trends over months are more reliable than any single reading.
Why the WHO data
The WHO Child Growth Standards, published in 2006 after the Multicentre Growth Reference Study, are the international benchmark in pediatric care. Not every online calculator uses them; older or regional references give different numbers for the same baby. That’s why Storklet tracks growth on this exact data: log a weight and it plots directly onto the growth curves, showing the percentile instantly alongside length, head circumference, feeding, sleep, and vaccines on one private timeline. See the growth and milestones tracker for the full picture, or browse all Storklet features.
Sources and Further Reading
We base our explainers on high-quality academic research and public health standards.
- The WHO Child Growth Standards, published in 2006, come from the Multicentre Growth Reference Study, which measured healthy breastfed children in Brazil, Ghana, India, Norway, Oman, and the United States between 1997 and 2003. WHO: Child Growth Standards MGRS study design↩
- The weight-for-age tables run from birth to 24 months in one-month steps, published separately for boys and girls with percentile columns from the 3rd to the 97th. WHO: weight-for-age tables↩
- The 3rd and 97th percentile lines sit at roughly two standard deviations from the median, which is why about 94% of healthy babies land between them. The outer bands are screening flags, not diagnosis. WHO training course on child growth assessment↩
- The standards are computed day by day, one set of values per day of age; the month-level tables here are a rounding convenience for quick lookups. WHO: Child Growth Standards↩
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