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Weight-for-Age Percentile Calculator (WHO, 5-10 Years)

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WHO Weight-for-Age Growth Chart (5-10 Years)

Plot a school-age child's weight against WHO Growth Reference 2007 data for ages 5-10 years. The chart displays the standard percentile curves (3rd, 15th, 50th, 85th, 97th) with your child's measurement pinned on top. WHO publishes weight-for-age LMS parameters only through age 10 because adolescent weight is better interpreted through BMI-for-age.

LMS Method: Z = ((X/M)^L − 1) / (L × S), percentile = Φ(Z) × 100

How It Works

The WHO 5-10 weight-for-age chart converts a single weight measurement into a percentile that answers "out of 100 WHO-reference children of the same age and sex, how many weigh less than mine?" Under the hood the calculator looks up three LMS parameters — L (skewness), M (median weight in kg), and S (coefficient of variation) — from the WHO Growth Reference 2007 table for the child's exact age in months, computes a Z-score with the Box-Cox equation Z = ((X/M)^L − 1) / (L × S), and maps the Z-score through the standard normal CDF to a percentile. The WHO weight-for-age table covers months 60 through 120 (5 to 10 years) in 1-month steps, so fractional ages are handled by linear interpolation between adjacent rows. Beyond age 10, WHO does not publish weight-for-age parameters — adolescent weight changes with puberty and height, so BMI-for-age (5-19) becomes the recommended screening tool.

Example Problem

A 7-year-old boy weighs 22.9 kg at his annual check-up. Where does he fall on the WHO 5-10 weight-for-age chart?

  1. Record the child's date of birth and the date of today's measurement — about 7 years (84 months) apart — and note the sex as Boy.
  2. Convert the weight to kilograms if it was recorded in pounds. Here it is already 22.9 kg, so no conversion is needed.
  3. Look up the WHO 5-19 LMS triple for boys at 84 months: L ≈ -0.46, M ≈ 22.89 kg, S ≈ 0.142.
  4. Compute the Z-score with Z = ((X/M)^L − 1) / (L × S). Substituting gives Z ≈ ((22.9/22.89)^-0.46 − 1) / (-0.46 × 0.142) ≈ 0.00.
  5. Map the Z-score through the standard normal CDF: Φ(0.00) ≈ 0.50, so the percentile is about the 50th.
  6. Report the result: a 7-year-old boy at 22.9 kg sits right at the WHO median — half of reference boys his age weigh less, half weigh more.

Key Concepts

A percentile is a rank, not a grade. The 75th percentile means 75% of WHO-reference children of the same age and sex weigh less — it does not mean the child is "75% healthy" or "25% overweight." Most pediatricians treat the 3rd-to-97th percentile band as the normal range for weight-for-age, and focus on trajectory over time rather than any single reading. The WHO Growth Reference 2007 differs from the WHO Child Growth Standards (0-5 years): the 5-19 data is descriptive (reconstructed from historical WHO, NCHS, and CDC data to match the 0-5 standards at the 5-year boundary), while the 0-5 data is prescriptive (based on optimal growth in exclusively breastfed children). Weight-for-age in the 5-10 year range should always be interpreted alongside height-for-age, and once a child approaches puberty, BMI-for-age becomes the better screening tool because it accounts for the rapid height and body-composition changes of adolescence.

Applications

  • Well-child visits from age 5 through age 10 — pediatricians plot each weight measurement to confirm steady growth along the child's usual channel.
  • Screening for underweight (persistent tracking below the 3rd percentile) in school-age children — often a prompt to evaluate nutrition, malabsorption, or chronic illness.
  • International weight comparison — the WHO reference is used worldwide and is the standard in most non-US pediatric guidelines.
  • School health programs and nutritional assessments in low- and middle-income country settings.
  • Complementary assessment alongside WHO height-for-age (5-19) and WHO BMI-for-age (5-19).
  • Transitioning from the WHO 0-5 weight-for-age chart at the 5-year boundary.

Common Mistakes

  • Using this chart for children over 10 — WHO does not publish weight-for-age parameters beyond 120 months. Switch to BMI-for-age (5-19 years) for older children.
  • Using weight-for-age alone to screen for obesity — BMI-for-age is the WHO-recommended screening tool because it accounts for height.
  • Confusing the WHO Growth Reference 2007 (5-19, descriptive) with the WHO Child Growth Standards (0-5, prescriptive) — they use different LMS tables even though both are "WHO" references.
  • Mixing the WHO reference with the CDC reference — the two curves differ by a few percentile points, and a child at the 50th WHO may be at the 55th CDC.
  • Not converting units — always verify whether the weight was recorded in kilograms or pounds before entering it.
  • Reading a one-off measurement as a diagnosis — trajectory across 2-3 visits is almost always more meaningful than a single point.

Frequently Asked Questions

Why does WHO weight-for-age stop at age 10?

WHO weight-for-age stops at age 10 because puberty introduces wide individual variation in muscle, fat, and bone mass that weight alone cannot interpret well. For ages 5–10, the chart shows where a child's weight ranks against the WHO 2007 reference. After age 10, BMI-for-age becomes the recommended weight-status screen, and height-for-age covers stature monitoring through age 19.

Why does this calculator stop at age 10 — other charts go to 19?

The WHO Growth Reference 2007 publishes height-for-age and BMI-for-age parameters through age 19, but weight-for-age only through age 10 (120 months). WHO explicitly omits adolescent weight-for-age because, during puberty, weight changes dramatically with height and body composition — a tall, muscular 14-year-old and a short, slender 14-year-old of the same weight fall at very different places on a weight-only chart. Instead, WHO recommends BMI-for-age (5-19) for children and teens over age 10 because BMI combines weight and height into a single index that adjusts for stature.

What is the 50th percentile weight for a 7-year-old?

On the WHO 5-10 chart, the 50th-percentile weight for a 7-year-old (84 months) boy is approximately 22.9 kg (50.5 lb) and for a 7-year-old girl is about 22.2 kg (48.9 lb). The 50th percentile is the WHO median — half of reference children of the same age and sex weigh more, half weigh less. It is not a target every child should hit; tracking consistently in your own channel matters more than landing on the 50th.

What is the difference between the WHO and CDC weight-for-age charts?

The CDC 2000 growth charts are built from US NHANES survey data collected between 1963 and 1994, and the AAP recommends them for US children from age 2 onward. The WHO Growth Reference 2007 is used internationally and blends historical WHO, NCHS, and CDC data into a reference that aligns smoothly with the WHO 0-5 standards at age 5. The two charts usually agree within a few percentile points, but the WHO curves are slightly lower than the CDC curves at many ages — so a child at the 50th WHO may land near the 55th on the CDC chart. For US clinical care follow your pediatrician; for international or research use, WHO is the default.

Is weight-for-age the right chart to screen for obesity?

No. WHO and the AAP both recommend BMI-for-age as the primary obesity screening tool from age 2 onward because BMI combines weight and height into a single index. Weight-for-age alone can flag extremes, but a tall child at the 90th weight percentile may have a perfectly healthy BMI, while a short child at the 70th weight percentile may be overweight. Use this chart alongside a BMI-for-age reading, not in isolation.

What should I do when my child turns 10?

Switch to the WHO BMI-for-Age (5-19 years) calculator once your child reaches 10 years and 1 month. BMI-for-age is the WHO-recommended indicator of weight status for the 5-19 range and is the tool most pediatricians use for pre-adolescent and adolescent weight screening. If you want continued US-style weight-for-age tracking beyond 10, the CDC 2-20 Weight-for-Age chart extends to age 20.

What weight percentile is considered healthy?

Most pediatricians treat the 3rd-to-97th percentile band as the normal weight-for-age range. What matters more than hitting a specific percentile is consistent tracking — a child steady on the 15th or the 85th is growing well. Crossing two or more major percentile bands in either direction over a few visits is the more common reason for clinical follow-up. For obesity screening specifically, WHO uses BMI-for-age ≥ 95th percentile as the threshold, not weight-for-age.

What if my child is below the 3rd percentile for weight?

A consistent reading below the 3rd percentile (Z-score under about -1.88) is outside the WHO normal range and warrants a discussion with your pediatrician. The clinical question is always "is this a stable channel for this child, or a new drop from a higher channel?" A child who has always tracked at the 2nd and is otherwise thriving is very different from a child who was at the 40th last year and is at the 2nd today. Possible causes for a drop include malnutrition, malabsorption, thyroid disease, and chronic infection.

Reference: WHO Growth Reference 2007, World Health Organization. https://www.who.int/tools/growth-reference-data-for-5to19-years

Worked Examples

Kindergarten check-up

Where does a 5-year-old girl weighing 18 kg fall on the WHO chart?

A pediatrician is reviewing a healthy 5-year-old girl at her well-child visit. Her recorded weight is 18.0 kg (39.7 lb) and the provider wants a quick WHO-reference percentile read.

  1. Knowns: age 60 mo (5.0 yr), sex girl, weight 18.0 kg
  2. WHO 5-19 LMS at 60 mo (girls): L ≈ -0.47, M ≈ 18.08 kg, S ≈ 0.142
  3. Z = ((18.0 / 18.08)^-0.47 − 1) / (-0.47 × 0.142) ≈ 0.03
  4. Φ(0.03) ≈ 0.51

~51st percentile — right at the WHO median and squarely in the healthy range.

A single reading at the 51st percentile is unremarkable; pediatricians watch whether she continues tracking that channel at future visits.

Elementary-school screening

An 8-year-old boy weighs 58 lb at his school physical — what percentile?

A parent brings their 8-year-old son in for his school physical. The scale reads 58.0 lb. The WHO 5-10 chart converts pounds to kilograms internally (58.0 lb × 0.4536 = 26.31 kg) and computes the percentile.

  1. Knowns: age 96 mo (8.0 yr), sex boy, weight 58.0 lb → 26.31 kg
  2. WHO 5-19 LMS at 96 mo (boys): L ≈ -0.53, M ≈ 25.83 kg, S ≈ 0.148
  3. Z = ((26.31 / 25.83)^-0.53 − 1) / (-0.53 × 0.148) ≈ 0.13
  4. Φ(0.13) ≈ 0.55

~55th percentile — a touch above the WHO median, still comfortably inside the normal range.

Weight-for-age is a screening input, not a diagnosis. Pair a mid-range percentile with height-for-age to judge proportionality before drawing conclusions.

End-of-range assessment

A 10-year-old boy weighs 38 kg — where is he on the WHO chart?

A pediatrician is assessing a 10-year-old boy at his final WHO weight-for-age-eligible visit. His weight is 38.0 kg (83.8 lb). This is the upper age boundary of the WHO weight-for-age table, so the next visit will need to switch to BMI-for-age.

  1. Knowns: age 120 mo (10.0 yr), sex boy, weight 38.0 kg
  2. WHO 5-19 LMS at 120 mo (boys): L ≈ -0.68, M ≈ 31.16 kg, S ≈ 0.163
  3. Z = ((38.0 / 31.16)^-0.68 − 1) / (-0.68 × 0.163) ≈ 1.10
  4. Φ(1.10) ≈ 0.86

~86th percentile — above average but inside the 3rd-to-97th normal band.

This is the upper edge of the WHO weight-for-age reference. At the next visit, switch to WHO BMI-for-Age (5-19) because adolescent weight is best interpreted alongside height.

How the percentile is calculated

The calculator turns one weight measurement into a percentile in three stages. First, it looks up three WHO parameters — L, M, and S — from the WHO Growth Reference 2007 table for the child's exact age (in months) and sex. L is the Box-Cox power transform (it accounts for the skew in childhood weight distributions), M is the median weight at that age, and S is the coefficient of variation. Second, it plugs those parameters into the Z-score formula:

Z score equals the quantity X divided by M, raised to the power L, minus 1, divided by L times S.

Where:

  • X — the child's measured weight in kilograms.
  • M — the WHO median weight at that age and sex.
  • L — the Box-Cox skewness parameter.
  • S — the coefficient of variation (a scaled standard deviation).

Third, the Z-score is mapped to a percentile through the standard normal cumulative distribution function, Φ(Z). A Z of 0 maps to the 50th percentile, -1.88 to the 3rd, and +1.88 to the 97th. The WHO weight-for-age table spans ages 60 to 120 months in 1-month steps, so fractional ages are handled by linearly interpolating L, M, and S between the two bracketing rows.

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