Baby & Child Growth Percentile Calculator
Enter your child's sex, age and a recent measurement. You get the percentile for length or height, weight, BMI and head size on the same WHO and CDC charts pediatricians in the US use, a growth curve you can add measurements to, and the PatPat clothing size that fits now and three and six months from now.
What you will see
- Percentiles for length or height, weight, weight-for-length or BMI, and head size
- A growth curve with the WHO or CDC percentile lines, plus any measurements you save
- The PatPat size that fits today, in 3 months and in 6 months
How to read your baby's percentile
A percentile places one measurement inside a large reference group of children of the same sex and age. A baby on the 30th percentile for weight weighs more than 30 in 100 babies that age and less than the other 70. It is a position, not a grade: the 30th percentile is not “underweight”, and the 90th is not “too big”. Most children sit somewhere between the 3rd and the 97th.
What a pediatrician looks at is the line over time. By the end of the first year or two, most healthy children settle into a channel between two of the main percentile lines and follow it. One reading tells you where your child is today; three or four readings a few months apart tell you whether growth is steady.
Small swings usually come from the measurement, not the child. A kicking baby can easily read a centimeter longer or shorter, and at six months one centimeter moves a baby near the middle of the chart by up to 18 percentile points. Weigh at the same time of day in a dry diaper, and measure length lying flat with a second adult holding the head against a wall or headboard.
What the calculator gives you
- Length-for-age (under 2, measured lying down) or height-for-age (2 and over, standing)
- Weight-for-age
- Weight-for-length under 2, BMI-for-age from 2 — how weight relates to size, which says more than weight alone
- Head circumference-for-age up to 5 years, if you enter it
Height percentile for boys and girls by age
Boys and girls are compared on separate charts because they grow on different schedules. Girls are a little shorter on average through early childhood, pull level or ahead around 10 to 12 when their growth spurt starts earlier, and stop growing sooner. The table shows the median (50th percentile) at common ages. The calculator itself uses the full curve, worked out to your child's exact age.
| Age | Boys height | Boys weight | Girls height | Girls weight |
|---|---|---|---|---|
| Birth | 49.9 cm (19.6 in) | 3.3 kg (7.3 lb) | 49.1 cm (19.3 in) | 3.2 kg (7.1 lb) |
| 3 months | 61.4 cm (24.2 in) | 6.4 kg (14.1 lb) | 59.8 cm (23.5 in) | 5.8 kg (12.8 lb) |
| 6 months | 67.6 cm (26.6 in) | 7.9 kg (17.4 lb) | 65.7 cm (25.9 in) | 7.3 kg (16.1 lb) |
| 9 months | 72.0 cm (28.3 in) | 8.9 kg (19.6 lb) | 70.1 cm (27.6 in) | 8.2 kg (18.1 lb) |
| 12 months | 75.7 cm (29.8 in) | 9.6 kg (21.2 lb) | 74.0 cm (29.1 in) | 8.9 kg (19.6 lb) |
| 18 months | 82.3 cm (32.4 in) | 10.9 kg (24.0 lb) | 80.7 cm (31.8 in) | 10.2 kg (22.5 lb) |
| 2 years | 86.5 cm (34.1 in) | 12.7 kg (28.0 lb) | 85.0 cm (33.5 in) | 12.1 kg (26.7 lb) |
| 3 years | 95.0 cm (37.4 in) | 14.3 kg (31.5 lb) | 93.9 cm (37.0 in) | 13.9 kg (30.6 lb) |
| 4 years | 102.2 cm (40.2 in) | 16.2 kg (35.7 lb) | 100.8 cm (39.7 in) | 15.8 kg (34.8 lb) |
| 5 years | 108.9 cm (42.9 in) | 18.4 kg (40.6 lb) | 107.7 cm (42.4 in) | 17.9 kg (39.5 lb) |
| 6 years | 115.4 cm (45.4 in) | 20.7 kg (45.6 lb) | 114.7 cm (45.2 in) | 20.2 kg (44.5 lb) |
| 8 years | 127.9 cm (50.4 in) | 25.6 kg (56.4 lb) | 127.6 cm (50.2 in) | 25.6 kg (56.4 lb) |
| 10 years | 138.6 cm (54.6 in) | 31.9 kg (70.3 lb) | 138.0 cm (54.3 in) | 32.9 kg (72.5 lb) |
| 12 years | 149.1 cm (58.7 in) | 40.5 kg (89.3 lb) | 151.2 cm (59.5 in) | 41.6 kg (91.7 lb) |
| 14 years | 163.8 cm (64.5 in) | 51.0 kg (112.4 lb) | 160.4 cm (63.1 in) | 49.4 kg (108.9 lb) |
| 16 years | 173.5 cm (68.3 in) | 60.9 kg (134.3 lb) | 162.5 cm (64.0 in) | 53.9 kg (118.8 lb) |
| 18 years | 176.2 cm (69.4 in) | 67.2 kg (148.2 lb) | 163.1 cm (64.2 in) | 56.2 kg (123.9 lb) |
Median (50th percentile). Birth to 18 months: WHO standards (length, lying down). 2 years and older: CDC 2000 charts (height, standing). The charts continue to age 20.
Height is the steadiest of the measurements. Weight reacts to a stomach bug or a growth spurt within weeks; height rarely changes channel after the second birthday. That is why a clear move across height lines deserves a second measurement more than a jump in weight does.
Wondering how tall your child will end up? Height percentile and adult height are related, but the parents' heights matter as much. Our Child Height Predictor combines both.
WHO vs CDC growth charts: which one this calculator uses
In the US, the CDC recommends the WHO growth standards from birth to 2 years and the CDC 2000 growth charts from 2 to 20 years. The calculator follows that rule on its own: you never have to pick a chart.
The two were built differently. The WHO standards followed healthy, mostly breastfed children in Brazil, Ghana, India, Norway, Oman and the United States, raised in conditions that let them grow well; they describe how children should grow. The CDC charts are a reference drawn from US national health surveys from the 1960s to the 1990s; they describe how American children did grow. Under 2, breastfed babies track WHO curves better, which is the main reason for the switch.
The charts also mark their edges differently. On WHO charts the usual cue for a closer look is below the 2nd or above the 98th percentile; on CDC charts it is below the 5th or above the 95th. Because the reference changes at the second birthday, a toddler can move a few percentile points at that visit without growing any differently. Standing height is also about 0.7 cm shorter than lying length in the same child, which adds to the dip.
Toddler and child growth chart: what changes after age 2
Growth slows down fast. A median boy grows about 25.9 cm in his first year and 12.1 cm in his second, then roughly 7.3 cm a year at ages 3 to 4 and 5.9 cm a year from 5 to 10, until the pubertal growth spurt.
From age 2, weight-for-length gives way to BMI-for-age. Children's BMI naturally falls from around their first birthday to about age 5 or 6 and then rises again, so the same BMI means something different at 3 than at 8, and adult BMI categories do not apply. The percentile is the number to read, not the BMI itself.
The toddler percentile stays useful as long as you measure the same way each time: shoes off, heels, bottom and shoulders against a wall, a book laid flat on the head, a mark on the wall, then measure the mark.
From percentile to clothing size
Baby and kids' clothes are cut to height ranges, and the age on the label is only the age a typical child reaches that height. A 9-month-old boy on the 90th percentile for length is about 74.8 cm and wears 9-12 M; one on the 10th is about 69.1 cm and still wears 6-9 M. So the calculator turns the length or height you enter into a PatPat size, using the height ranges from our official size charts, the same figures shown on every product page.
The “in 3 months” and “in 6 months” sizes assume your child stays on the same height percentile and read the size off that projected height. After the first year children rarely change channel, so it is a fair way to buy a season ahead, a winter coat in September or holiday pajamas in November. In the first months babies still drift between lines, so treat the projection as a rough guide. When a height lands within 1 cm of the top of a size, we suggest the next one up.
The table lists each size with its height range and the age at which a median boy and a median girl are that tall.
| PatPat size | Height range | Median boy fits it at | Median girl fits it at |
|---|---|---|---|
| Newborn | 45.7–55.9 cm (18.0–22.0 in) | 0 mo–1.3 mo | 0 mo–1.7 mo |
| 0-3 M | 55.9–61.0 cm (22.0–24.0 in) | 1.3 mo–2.8 mo | 1.7 mo–3.5 mo |
| 3-6 M | 61.0–68.6 cm (24.0–27.0 in) | 2.8 mo–6.6 mo | 3.5 mo–7.9 mo |
| 6-9 M | 68.6–73.7 cm (27.0–29.0 in) | 6.6 mo–10.4 mo | 7.9 mo–11.8 mo |
| 9-12 M | 73.7–78.7 cm (29.0–31.0 in) | 10.4 mo–14.6 mo | 11.8 mo–16.1 mo |
| 12-18 M | 78.7–83.8 cm (31.0–33.0 in) | 14.6 mo–19.6 mo | 16.1 mo–21.2 mo |
| 18-24 M / 2 Y | 83.8–88.9 cm (33.0–35.0 in) | 19.6 mo–2.3 yr | 21.2 mo–2.4 yr |
| 3 Y | 88.9–99.1 cm (35.0–39.0 in) | 2.3 yr–3.6 yr | 2.4 yr–3.8 yr |
| 3-4 Y | 99.1–104.1 cm (39.0–41.0 in) | 3.6 yr–4.3 yr | 3.8 yr–4.5 yr |
| 4-5 Y | 104.1–111.8 cm (41.0–44.0 in) | 4.3 yr–5.4 yr | 4.5 yr–5.6 yr |
| 5-6 Y | 111.8–116.8 cm (44.0–46.0 in) | 5.4 yr–6.2 yr | 5.6 yr–6.3 yr |
| 6-7 Y | 116.8–121.9 cm (46.0–48.0 in) | 6.2 yr–7 yr | 6.3 yr–7.1 yr |
| 7-8 Y | 121.9–129.5 cm (48.0–51.0 in) | 7 yr–8.3 yr | 7.1 yr–8.3 yr |
| 8-9 Y | 129.5–134.6 cm (51.0–53.0 in) | 8.3 yr–9.2 yr | 8.3 yr–9.3 yr |
| 9-10 Y | 134.6–139.7 cm (53.0–55.0 in) | 9.2 yr–10.2 yr | 9.3 yr–10.3 yr |
| 10-11 Y | 139.7–144.8 cm (55.0–57.0 in) | 10.2 yr–11.2 yr | 10.3 yr–11.1 yr |
| 11-12 Y | 144.8–152.4 cm (57.0–60.0 in) | 11.2 yr–12.5 yr | 11.1 yr–12.2 yr |
| 12-13 Y | 152.4–157.5 cm (60.0–62.0 in) | 12.5 yr–13.2 yr | 12.2 yr–13.1 yr |
| 13-14 Y | 157.5–163.8 cm (62.0–64.5 in) | 13.2 yr–14 yr | from 13.1 yr |
Height ranges from PatPat's official baby and kids size charts. Ages are when a child on the 50th percentile is that tall; a taller or shorter child reaches each size earlier or later.
When to talk to your pediatrician
Bring it up at the next visit, or call sooner if you are worried, when:
- a reading lands outside the usual range for the chart (WHO: below the 2nd or above the 98th; CDC: below the 5th or above the 95th) and a careful re-measure confirms it;
- height or weight crosses two of the main percentile lines between check-ups, in either direction;
- weight is falling across lines while length keeps rising;
- head circumference changes channel quickly in the first year.
None of these is a diagnosis. A doctor re-measures with clinic equipment and looks at things this page cannot: the parents' heights, birth weight, feeding, illness and how your child is doing overall. A home tape measure is less precise than a clinic stadiometer, and a percentile is a starting point for that conversation, not a verdict.
Growth percentile FAQ
What percentile is normal for a baby?
Any percentile between roughly the 3rd and the 97th is within the range most healthy babies fall in. The 50th is the median, not a target. What matters more is that your baby follows a similar line over several measurements.
Is the 90th percentile too big, or the 5th too small?
Not on its own. Some children are simply large or small, often like their parents. Doctors look at whether the line is steady and whether height and weight are in proportion. A reading outside the usual range or a fall across two main lines is the cue for a closer look.
Can a percentile predict how tall my child will be?
Only loosely in the first year. From around age 2 to 3, height percentile becomes a better guide, but parents' heights matter as much. The Child Height Predictor combines current height with both parents' heights for an estimate.
How often should I measure my child?
Pediatric check-ups in the US measure at 1, 2, 4, 6, 9, 12, 15, 18, 24 and 30 months, then once a year. At home, once a month is plenty for a baby and every few months for an older child. More often mostly measures noise.
How do I calculate percentiles for a premature baby?
Use corrected age: the age your baby would be if born at 40 weeks. Tick “Born before 37 weeks” and enter the weeks of pregnancy at birth, and the calculator subtracts the difference. Corrected age is usually used until 24 months.
Why did my child's percentile drop?
The most common reasons are a measurement difference, the switch from lying length to standing height at age 2, and, in the US, the switch from WHO to CDC charts at the same age. In the first two years babies also often drift toward their own channel. A drop across two main lines that a re-measure confirms is worth raising with your pediatrician.
Why do WHO and CDC charts give different results?
They describe different groups of children: WHO healthy children raised in good conditions in six countries, CDC US children measured in national surveys. For the same measurement the percentile can differ by a few points, most of all in weight.
What size should a baby on the 75th percentile wear?
It depends on age, because sizes are cut to height. For example, a 6-month-old boy on the 75th percentile for length is about 69.1 cm (27.2 in) long, which is PatPat size 6-9 M. Enter your child's own length above to get the size and the next two.
Data sources and method
Percentiles are calculated with the LMS method (Cole & Green, 1992): each chart gives three values per age (L, M and S) and the z-score is ((value / M)L − 1) / (L × S), interpolated to the exact age. For weight, weight-for-length and BMI beyond ±3 SD, the WHO's restricted method is applied.
- Birth to 2 years, plus head circumference to 5 years: WHO Child Growth Standards (2006)
- 2 to 20 years: CDC 2000 Growth Charts (National Center for Health Statistics)
- Clothing sizes: PatPat official size charts, as shown on each product page (checked 2026-09-04)
We checked the calculator against the published WHO tables and the CDC's WHO percentile files: across 3,599 test points, results match to within 0.1 percentile points. This page is general information for parents. It is not medical advice and does not replace a check-up.
