Child Growth and Weight by Age: Charts and Percentiles

Almost every parent has at some point compared their child with someone else's and drawn a conclusion about health. A paediatrician looks differently: not at one point but at a line. A child steadily tracking just below average for two years is healthy. A child who was above average and slid to the lower boundary in six months needs review — even if formally still "within normal".

Child growth and weight by age: reference charts

The figures below are averages (roughly the 50th percentile). A deviation of 10–15% either way means nothing on its own.

Rates matter more than absolute numbers: a child gains about 25 cm in the first year, 12 in the second, then 5–6 cm a year until puberty.

Growth percentiles: why they beat average numbers

A percentile shows how many children of the same age and sex are smaller. The 25th percentile means 25% are shorter or lighter and 75% are taller or heavier. Normal spans the 3rd to 97th percentile.

Three practical rules follow:

1. Not being on the 50th percentile is normal. Someone has to be on the 10th, and that is not a disease.
2. Stability of the channel is what counts. A child holding their 15th percentile is growing normally.
3. Crossing channels is the concern. A downward move through two centile channels is a signal even while absolute numbers still look normal.

The ratio is assessed separately: if weight falls before height, nutrition and losses are usually considered; if height slows while weight holds, hormonal causes come first.

Newborn weight gain and the first year

In the first days a baby loses up to 7–10% of body mass — this is physiological. Birth weight is regained by day 10–14; if not, feeding is reviewed.

Then the reference gains are:

Useful checkpoints: birth weight doubles by 4–5 months and triples by one year.

How to measure a child's height correctly

Half the "deviations" seen at appointments are measurement errors.

• Under 2 years, measure lying down on a length board, with two people: one holds the head, the other straightens the legs.
• Over 2 years, standing, without shoes, heels together, with the back of the head, shoulder blades, buttocks and heels touching the wall, gaze level.
• Switching from lying to standing produces a 0.5–1 cm difference in favour of the former. That is not a halt in growth.
• Weigh at the same time of day, undressed for infants.

Underweight children and growth faltering

What concerns is the pattern rather than the numbers:

• weight not increasing for two months or more in the first year;
• a downward move through two centile channels;
• height below the 3rd percentile or well below the parental prediction;
• weight falling while height still holds — typical of undernutrition and chronic losses: coeliac disease, persistent diarrhoea, long-standing constipation with reduced appetite;
• height slowing with normal weight — more often endocrine, including hypothyroidism.

In infants, feeding problems sometimes drive poor gain and are read by parents as fussiness and colic — that fork is described in infant colic.

Overweight children and BMI in children

Adult BMI thresholds (25 and 30) do not apply to children: body composition and proportions change with age. Over age 2, BMI for age and sex is used: overweight above the 85th percentile, obesity above the 95th.

In practice the trend matters more: a steady climb across BMI percentiles over a year is a stronger signal than a single high reading. Early action here is about family eating patterns and activity, not diets for the child.

When tests are needed

Growth and weight themselves need no tests — this is a clinical assessment. Investigation follows a departure from the trajectory:

• a complete blood count to exclude anaemia — paediatric ranges are in CBC in children and iron deficiency in iron deficiency anaemia; the key markers are haemoglobin and ferritin;
• a thyroid panel with free T4 when height slows;
• coeliac antibodies when poor gain comes with abdominal complaints;
• vitamin D, calcium and alkaline phosphatase when rickets is suspected, especially with night sweating — see child sweating in sleep.

A scheduled age-appropriate check-up can be assembled as one list by the check-up selector. Tooth eruption timing, often checked against norms as well, is covered in teething in children.

This article is informational. Physical development is assessed by a paediatrician.