How do I calculate my child's weight percentile?

Enter your child's age, sex, and weight into a weight percentile calculator. The tool compares that measurement with WHO references in infancy and CDC references after age 2, then estimates the percentile. You can use this page for an instant result instead of plotting the point manually on a paper growth chart.

Is the 10th percentile underweight for a child?

Not necessarily. The 10th percentile is still within the normal reference range. A child at P10 may simply be naturally smaller than average, especially if height percentile is similar and the pattern has been steady. Underweight screening in children older than 2 usually relies more on BMI-for-age than weight percentile alone.

What weight percentile is considered overweight for a child?

Weight percentile by itself does not define overweight because it does not account for height. For children ages 2 to 20, clinicians usually use BMI-for-age instead. BMI at or above the 85th percentile suggests overweight risk, and BMI at or above the 95th percentile suggests obesity risk, which needs clinical interpretation.

Why does my child's weight percentile keep changing?

Weight percentile can shift in infancy, during recovery from illness, around growth spurts, and before or during puberty. Small changes are common. More concern comes when weight repeatedly crosses two major percentile channels, drifts away from height percentile, or changes quickly together with appetite problems, fatigue, or other symptoms.

Should I be worried if my child is at the 5th weight percentile?

A child who has always tracked near the 5th percentile may simply have a smaller natural build. Concern rises when the child drops down to that level from a higher percentile, stops gaining weight as expected, or shows poor growth in height too. A pediatric clinician can judge whether the pattern fits family size and health history.

Weight Percentile Calculator for Children

This weight percentile calculator uses WHO and CDC growth standards to show where your child's weight ranks compared to other children of the same age and sex. Enter your child's age, sex, and weight below to get an instant percentile result, or open the full growth chart calculator for a broader height, weight, and BMI view.

✓ WHO standards for ages 0-2
✓ CDC growth data for ages 2-20
✓ Instant results — no sign-up needed

Weight Percentile Calculator

This embedded version keeps the full 0 to 20 year age range, starts at age 5, automatically swaps from WHO to CDC references, and puts weight percentile first. Height and BMI remain visible because weight-for-age becomes much more useful when you compare it with body build and growth pattern.

Percentile results

Current percentile summary

Using: CDC

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Interactive charts

Visualize the current percentile position

Chart type

Metric

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Weight-for-Age Reference Table

Use the tabs below to compare boys and girls across key weight-for-age rows from birth through age 20. This is a quick lookup table, not a diagnosis tool. If you want a broader reference view, see average weight by age plus age-specific guides like average weight for a 1 year old, average weight for a 2 year old, and average weight for a 5 year old.

Boys Weight-for-Age Reference

P3 / P10 / P50 / P90 / P97 rows in kg

Weight-for-age reference rows using WHO standards from birth to 24 months and CDC growth charts from age 2 to 20 years.
Age	P3	P10	P50	P90	P97
Birth	2.5	2.8	3.3	4.0	4.4
3 mo	5.0	5.5	6.4	7.4	8.0
6 mo	6.4	7.0	7.9	9.0	9.8
9 mo	7.1	7.8	9.2	10.7	11.9
12 mo	7.7	8.5	9.6	11.0	12.0
18 mo	8.8	9.7	10.9	12.5	13.7
2 yr	10.4	11.3	12.7	14.4	15.6
3 yr	11.8	12.6	14.3	16.3	17.9
4 yr	13.2	14.2	16.2	18.7	20.9
5 yr	14.8	15.9	18.4	21.6	24.3
6 yr	16.2	17.6	20.5	24.6	27.9
7 yr	17.6	19.3	22.9	28.0	32.0
8 yr	19.1	21.1	25.6	31.9	36.9
9 yr	20.8	23.2	28.6	36.4	42.3
10 yr	22.8	25.0	32.0	43.5	48.0
11 yr	25.0	27.9	35.6	48.0	54.0
12 yr	27.5	31.0	39.9	54.0	61.0
14 yr	35.0	40.0	51.0	66.0	76.5
16 yr	44.5	50.0	60.5	76.0	88.5
18 yr	49.5	55.5	65.5	82.0	94.5
20 yr	51.0	57.5	67.5	84.5	97.0

* P3/P10/P50/P90/P97 = 3rd, 10th, 50th, 90th, and 97th percentile.

* Data sources: WHO Multicentre Growth Reference Study (birth-24 months); CDC 2000 Growth Charts (age 2-20 years).

* This table is for reference only and does not constitute medical advice.

What Does a Weight Percentile Mean?

A percentile shows relative position, not a grade. P50 is the median weight for children of the same age and sex, while values anywhere from about P3 to P97 can still fall within a broad normal reference range. A child weight percentile calculator helps estimate weight for age percentile and can guide questions like is my child overweight, but weight alone never tells the full story. Pediatric interpretation should still compare weight with height percentile and, after age 2, BMI-for-age.

Average Weight by Age — Boys and Girls Overview

Average weight (P50) at key ages

Age	Boys	Girls
Birth	3.3 kg (7.3 lbs)	3.2 kg (7.1 lbs)
6 months	7.9 kg (17.4 lbs)	7.3 kg (16.1 lbs)
1 year	9.6 kg (21.2 lbs)	9.0 kg (19.8 lbs)
2 years	12.7 kg (28.0 lbs)	12.1 kg (26.7 lbs)
5 years	18.4 kg (40.6 lbs)	17.9 kg (39.5 lbs)
10 years	32.0 kg (70.5 lbs)	32.5 kg (71.7 lbs)
15 years	56.5 kg (124.6 lbs)	52.5 kg (115.7 lbs)

Average weight by age child tables are best read from the P50 line, but average alone is only a center point. An average child weight chart for boys and girls helps you see how quickly typical weight changes through infancy, childhood, and adolescence, especially at milestone ages where parents often compare growth with classmates or siblings. The full range matters more than the midpoint.

Weight-for-Age vs. BMI-for-Age — What's the Difference?

	Weight-for-Age	BMI-for-Age
What it measures	Weight relative to peers	Weight relative to height and age
Best for	Ages 0-2 and quick reference checks	Ages 2-20 for weight-status screening
Limitation	Doesn't account for height	Requires both height and weight
Used by	WHO infant charts and broad CDC reference review	CDC pediatric BMI charts

When parents compare weight for age vs BMI for age child measures, the key distinction is that BMI adds height back into the picture. For infants, weight-for-age is widely used because length and feeding status change quickly. After age 2, a BMI calculator for kids usually gives a better screening view than weight percentile alone, especially when asking whether a child may be underweight or overweight. The matching height percentile calculator is also helpful for context.

What Affects a Child's Weight Percentile?

Factors affecting child weight include genetics, diet quality, calorie intake, physical activity, sleep, puberty timing, chronic disease, and medications such as steroids. When parents ask why is my child gaining weight, the answer can involve more than food alone. Family body build, reduced activity after illness, stress, poor sleep, or rapid developmental changes may all shift the curve, so percentile trends should always be interpreted in broader clinical context.

How Weight Percentile Changes Over Time

A child weight growth pattern can change quickly in infancy, then often becomes steadier after age 2 before shifting again near puberty. That makes weight percentile tracking over time more useful than any single number. Crossing two major percentile channels deserves attention, particularly if weight starts to separate from height percentile or BMI rises faster than expected. For home tracking, measuring every 3 to 6 months is usually enough unless a clinician wants closer follow-up.

When to Talk to Your Pediatrician About Weight

Discuss with your pediatrician if:

• Weight is consistently below P3 or above P97
• Weight percentile drops or rises across 2+ major channels
• BMI-for-age is above P85 or P95
• Your child has poor appetite, excessive hunger, or rapid unexplained weight change

This section helps explain child underweight overweight percentile concerns, but it is still not a substitute for medical advice. Knowing when to worry about child weight depends on growth pattern, nutrition, symptoms, puberty timing, and the child's broader medical history. Persistent low intake, fast gain, fatigue, abdominal symptoms, or a mismatch between weight and height all justify a clinical review rather than relying only on a chart.

Medical disclaimer

Weight percentile results are educational and depend on age, sex, measurement accuracy, and the selected WHO or CDC reference. Weight alone cannot diagnose overweight, underweight, or nutritional problems. Please review unusual growth patterns with a pediatric clinician.

Frequently Asked Questions

These FAQs cover normal percentile ranges, how the calculator works, why weight percentile changes, and when BMI matters more than weight-for-age alone. For broader answers, see our growth chart FAQ.

Many healthy children fall anywhere from about P3 to P97 on a weight-for-age chart. A percentile inside that range is not automatically good or bad. What matters most is the trend over time and whether weight still makes sense alongside height percentile, BMI-for-age, appetite, puberty timing, and overall health.

Related Growth Chart Tools

Height Percentile Calculator BMI Calculator for Kids Growth Chart Calculator Average Height & Weight by Age

Weight Percentile Calculator for Children

Weight Percentile Calculator

Weight-for-Age Reference Table

Boys Weight-for-Age Reference

What Does a Weight Percentile Mean?

Average Weight by Age — Boys and Girls Overview

Weight-for-Age vs. BMI-for-Age — What's the Difference?

What Affects a Child's Weight Percentile?

How Weight Percentile Changes Over Time

When to Talk to Your Pediatrician About Weight

Frequently Asked Questions

What is a normal weight percentile for a child?−

How do I calculate my child's weight percentile?+

Is the 10th percentile underweight for a child?+

What weight percentile is considered overweight for a child?+

Why does my child's weight percentile keep changing?+

Should I be worried if my child is at the 5th weight percentile?+

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