Child Weight Percentile Calculator

Five bands, one weight, one answer

Enter your child's sex, age and weight - the calculator returns a percentile rank based on WHO reference data for ages 2-18. A child at the 50th percentile weighs exactly the median: half of same-age, same-sex peers weigh less, half weigh more. The result falls into one of five bands: significantly below normal (below 3rd), below average but normal (3rd-15th), normal (15th-85th), above normal (85th-97th) and significantly above normal (above 97th).

Weight percentile is not a diagnosis. It is a screening tool that tells you where your child sits relative to population norms. A child at the 5th percentile who has always been at the 5th percentile is developing consistently. A child who drops from the 60th to the 10th percentile in six months warrants medical attention - even though the 10th percentile is technically "normal."

How to check your child's weight percentile - step by step

Sex - boys and girls have different weight norms at every age. Select the child's biological sex.
Age (years) - full years from 2 to 18. For infants under 2, consult your pediatrician directly.
Additional months - optional. Adding months (0-11) gives a more precise interpolation between yearly reference values.
Weight (kg) - weigh without shoes, in light clothing. Morning, on an empty stomach, gives the most consistent reading.
Read your results - the calculator shows the percentile rank, the weight category, a visual bar with the child's position and a reference table showing all five percentile thresholds for the child's age.

WHO weight reference table by age and sex

Median (50th percentile) weight for boys and girls at key ages. These are the reference values this calculator uses.

Age	Boys - 3rd	Boys - 50th	Boys - 97th	Girls - 3rd	Girls - 50th	Girls - 97th
3 yr	12.1 kg	14.7 kg	18.5 kg	11.6 kg	14.2 kg	18.0 kg
6 yr	16.5 kg	20.7 kg	28.1 kg	15.8 kg	20.0 kg	27.2 kg
10 yr	23.1 kg	30.7 kg	45.8 kg	22.1 kg	29.8 kg	44.6 kg
14 yr	35.0 kg	46.8 kg	67.0 kg	33.0 kg	44.8 kg	64.5 kg
18 yr	50.0 kg	63.5 kg	86.0 kg	41.0 kg	53.0 kg	72.5 kg

Weight percentile bands explained

Percentile range	Category	What it means
Below 3rd	Significantly below normal	Weighs less than 97% of peers - pediatrician evaluation recommended
3rd-15th	Below average (normal)	Lean but within healthy range - no concern if consistent
15th-85th	Normal	Healthy weight - the middle 70% of the population
85th-97th	Above normal	Heavier than 85% of peers - worth monitoring trends
Above 97th	Significantly above normal	Heavier than 97% of peers - pediatrician and dietitian assessment recommended

Practical examples

Example 1: Boy, 5 years old, 18.5 kg
Percentile: ~50th - Normal. Right at the median - the most average weight for a 5-year-old boy.

Example 2: Girl, 8 years old, 35 kg
Percentile: ~95th - Above normal. Above the 85th percentile threshold (29.2 kg). Monitoring recommended.

Example 3: Boy, 12 years old, 30 kg
Percentile: ~10th - Below average (normal). Below the 15th percentile (31.6 kg) but above the 3rd (27.8 kg). Lean but within healthy range.

Example 4: Girl, 3 years, 6 months, 17 kg
Percentile: ~90th - Above normal. Higher than the interpolated 85th percentile (~17.2 kg) for 3.5-year-old girls.

Example 5: Boy, 16 years old, 55 kg
Percentile: ~30th - Normal. Between the 15th (48.5 kg) and 50th (56.5 kg) - lean-normal build, typical for active teenagers.

FAQ - Frequently asked questions

What is a weight percentile?

A percentile is a ranking against a reference population of the same age and sex. If your child is at the 40th percentile, that means 40% of children of the same age and sex weigh less, and 60% weigh more. The 50th percentile represents the median - the exact middle.

Is a high percentile always bad?

Not necessarily. A child at the 90th percentile who has been tracking at the 85th-95th range since infancy is simply a bigger child. What matters most is consistency - sudden jumps or drops across percentile bands warrant attention. A tall child will naturally weigh more, which is why pediatricians also check weight-for-height (BMI percentile).

Weight percentile vs BMI percentile - which matters more?

Weight percentile tells you how your child's weight compares to peers of the same age. BMI percentile adjusts for height, so it is better at identifying over- or underweight. A tall, lean child might be at the 80th percentile for weight but only the 40th for BMI. For the most complete picture, pediatricians use both along with height percentile.

How accurate are WHO growth charts?

The WHO growth standards (used for children under 5) were developed from a multi-country study of children raised in optimal conditions - breastfed, non-smoking households, adequate nutrition. For ages 5-18, the WHO uses reference data (describing how children actually grow in a given population). The calculator uses approximate values derived from these references. For clinical decisions, your pediatrician uses official charts with more data points.

My child just turned 2. Is this calculator reliable for toddlers?

At age 2, growth patterns are still highly variable. The calculator covers ages 2-18 and uses interpolation for in-between ages. For children under 2, separate WHO weight-for-age charts exist that use monthly intervals rather than yearly. Your pediatrician will have these charts and can provide a more precise assessment for infants and young toddlers.

When should I see a doctor about my child's weight?

Consult a pediatrician if your child is below the 3rd or above the 97th percentile, if there has been a sudden change of two or more bands (e.g., from the 50th to the 15th in six months), or if your child shows signs of nutritional deficiency (fatigue, frequent illness, hair loss). A single reading outside normal range is not a diagnosis - the trend over time matters most.

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