# Child Growth Percentile Calculator Height-for-age and weight-for-age percentiles for ages 2 to 20, computed from the CDC 2000 growth chart LMS data. --- - **Canonical URL:** https://dothecalculation.com/calculators/child-growth-percentile-calculator - **Category:** Health and fitness - **Publisher:** Do The Calculation (https://dothecalculation.com) - **Cost:** Free, no account or sign-up required - **Privacy:** Runs entirely in the browser; inputs are never sent to a server - **Methodology:** https://dothecalculation.com/methodology --- ## Height and weight percentiles on the CDC growth charts Enter a child's age, sex, weight and standing height to see where each measurement falls on the CDC 2000 weight-for-age and stature-for-age charts, from 2 to 20 years. - Real CDC LMS reference data, not an approximated curve - Weight-for-age and stature-for-age, each with its z-score - A screening reference: the trend over time matters more than one point ## Quick Answer — What Percentile Is My Child's Height and Weight? A growth percentile tells you what share of children of the same age and sex in the CDC reference population measured below your child. The 50th percentile is the median; the 10th means 10% of the reference children were smaller. The CDC publishes three numbers, **L, M and S**, for every age from 24 to 240 months. The percentile comes from a z-score: **z = ((X ÷ M)^L − 1) ÷ (L × S)**, where X is the weight or height, and the z-score is converted with the standard normal distribution. **Worked example:** a boy aged exactly 8 years who weighs 25.5 kg and stands 128 cm tall is at the **48.6th percentile for weight** and the **50.8th percentile for height** — almost exactly on the median line for both. **This is a screening reference, not a diagnosis.** A single percentile says little on its own. A pediatrician looks at how a child's measurements track across several visits, measured the same way each time, together with the child's health, development and family. ## How to Use This Calculator: An 8-Year-Old Boy Choose **Boy**, set age to **8 years and 0 months** (96 months), and enter a weight of **25.5 kg** and a standing height of **128 cm**. You can switch to pounds and inches; the calculator converts to kilograms and centimetres before looking anything up. For weight, the calculator reads the CDC values for boys at 96 months: a median (M) of **25.64 kg**, with L = **−1.349** and S = **0.1556**. The weight of 25.5 kg is just under that median, giving z = **−0.04** and the **48.6th percentile**, between the 25th and 50th percentile lines printed on the chart. For height, the median at 96 months is **127.88 cm**, so 128 cm gives z = **0.02** and the **50.8th percentile**, between the 50th and 75th lines. The calculator also shows the 5th, 50th and 95th percentile values at that age. For this boy, the 5th to 95th percentile weight range is **20.6 kg to 35.1 kg**, and the height range is **118.6 cm to 137.6 cm**. That spread is the most useful thing on the page for a worried parent: the range of ordinary eight-year-olds is very wide. ## The Formulas and Reference Data This Calculator Uses **Reference data:** the CDC 2000 growth charts for the United States, from the National Center for Health Statistics. The CDC publishes the chart values as data files: **wtage.csv** for weight-for-age and **statage.csv** for stature-for-age. This calculator stores both files' L, M and S columns exactly as published, for boys and girls, from 24 to 240 months. **Age lookup:** the tables list values at exactly 24 months and then at each half month (24.5, 25.5, 26.5 and so on up to 239.5, then 240). For an age between two rows, L, M and S are **interpolated linearly** between the two nearest rows. **The LMS method:** each age has a skewness parameter L, a median M and a coefficient of variation S. The z-score is **z = ((X ÷ M)^L − 1) ÷ (L × S)**, a transformation described by T. J. Cole in 1990 that turns a skewed measurement into a normally distributed one. The percentile is **Φ(z) × 100**, where Φ is the standard normal cumulative distribution. **Percentile lines:** the 5th and 95th percentile values shown come from inverting the formula, **X = M × (1 + L × S × z)^(1/L)**, at z = ±1.645. **Checked against the CDC:** the published files also list the 3rd, 5th, 10th, 25th, 50th, 75th, 90th, 95th and 97th percentile values for every row. Feeding each of those values back into this calculator returns the matching percentile to within 0.00001 of a percentile point, for every row of both files. ## A Second Example: A 14½-Year-Old Girl Choose **Girl**, set age to **14 years and 6 months** (174 months), and enter **45 kg** and **150 cm**. Weight comes out at the **23.8th percentile** (z = −0.71), between the 10th and 25th lines. Height comes out at the **4.2nd percentile** (z = −1.73), between the 3rd and 5th lines. The median height for girls of this age is **161.27 cm**, so this girl is about **11.3 cm** below it. This is the kind of result that should be read carefully rather than alarmingly. Adolescence is when percentiles are least stable, because children go through their growth spurt at different ages. A girl who starts puberty later than average can sit low on the stature chart for a year or two and then climb back as she catches up. A girl who has already finished growing and sits at the same point will not. The number cannot tell those two situations apart. Only the pattern over time can, along with information a pediatrician collects: signs of puberty, the parents' heights, earlier measurements and general health. If the same girl still measured 150 cm at 18, she would be at the 2.2nd percentile — and that single comparison makes clear why growth is judged as a trajectory. ## How Pediatricians Read a Growth Chart Percentile lines are not targets. A child who has always tracked along the 10th percentile and continues to do so is growing consistently; being small is not in itself a problem. What prompts a closer look is a change in pattern, such as a child who moves steadily across the major percentile lines over several visits, or whose weight and height move in different directions. Measurement technique matters as much as the numbers. Height should be measured standing, without shoes, back against a wall or stadiometer, looking straight ahead. Home measurements with a tape against a door frame can easily be off by a centimetre or more, which is enough to move a percentile several points. Weight changes during the day with meals and clothing. The CDC recommends different charts for different ages. For children under 2 years, the CDC recommends the WHO growth standards, which describe how healthy breastfed infants grow; for ages 2 to 19, it recommends the CDC 2000 charts used here. That is why this calculator starts at 24 months. ## Limitations **Not a diagnosis.** A percentile, high or low, does not mean a child is unwell, and a percentile in the middle does not rule anything out. **A reference, not a standard.** The CDC 2000 charts describe how a sample of U.S. children grew in the decades the data came from. They show how children did grow, not how they ideally should grow. **Ages 2 to 20 only.** Under 2, use the WHO growth standards through your pediatrician. The calculator will not return a result outside 24 to 240 months. **Not for all children.** Children born very preterm and children with conditions that affect growth, such as Down syndrome, may need specialised charts. Ask the child's doctor which reference applies. **Weight-for-age does not describe body fat.** A tall child will naturally be heavier. To judge weight relative to height, a BMI-for-age percentile is the appropriate measure. ## Related Calculators This calculator gives weight-for-age and height-for-age. To judge whether a child's weight is proportionate to their height, use the [kids BMI percentile calculator](/calculators/kids-bmi-percentile-calculator), which applies the CDC BMI-for-age data to classify weight status; the two pages answer different questions and are most useful together. For adults, weight relative to height is assessed with the [adult BMI calculator](/calculators/bmi-calculator) instead of percentiles. Growth tracking starts before birth, too: the [pregnancy calculator](/calculators/pregnancy-calculator) lays out the timeline of a pregnancy, and the [gestational age calculator](/calculators/gestational-age-calculator) works out how far along a pregnancy is, which is also the basis for correcting a preterm baby's age on early growth charts. ## Frequently asked questions ### What does the 50th percentile mean? It is the median: half the children of the same age and sex in the CDC reference population measured below that value and half above. It is not a target. A child at the 20th or 80th percentile can be growing perfectly normally. ### Is a low percentile something to worry about? Not on its own. Many healthy children track consistently along a low or high percentile because of their family's build. Doctors look more closely when a child's measurements cross percentile lines over time, or when height and weight move in different directions. Discuss any concern with your pediatrician. ### How is this different from the kids BMI percentile calculator? This page shows height-for-age and weight-for-age separately. The kids BMI percentile calculator combines weight and height into BMI and compares it with the CDC BMI-for-age data, which is what is used to classify weight status as underweight, healthy weight, overweight or obesity. ### Why does the calculator start at age 2? The CDC recommends the WHO growth standards for children under 2 and the CDC 2000 charts from age 2. This calculator uses the CDC 2000 data files, which begin at 24 months and run to 240 months. ### Where does the reference data come from? From the CDC's published growth chart data files, wtage.csv and statage.csv, from the National Center for Health Statistics. They list the L, M and S parameters for every half month of age for boys and girls. This calculator stores those values exactly and reproduces the CDC's published percentile columns. ### How accurate do my home measurements need to be? More accurate than most people expect. For an 8-year-old boy, 1 cm of height is a noticeable move in percentile terms. Measure standing height without shoes, heels and back against a wall, with a flat object resting on the head, and weigh at a similar time of day in light clothing. ### Why did my teenager's height percentile drop? Most often because of puberty timing. Children who start their growth spurt later than average can drop in percentile for a while, then catch up. A 14½-year-old girl at 150 cm is at the 4.2nd percentile; the same height at 18 would be the 2.2nd. Only follow-up measurements and a pediatrician's assessment can tell which situation applies. ### Can I use this for a baby born prematurely? For young children born preterm, doctors often correct age for prematurity when plotting growth, and very preterm infants may be assessed on specialised charts. This calculator uses chronological age from 2 years, so ask your child's doctor how to interpret it. ## Related concepts - **LMS Method** — A way of describing a skewed growth distribution with three age-specific numbers: L (skewness), M (median) and S (coefficient of variation). It turns a measurement into a z-score. - **Z-Score** — How many standard deviations a measurement sits from the median after the LMS transformation. A z-score of 0 is the 50th percentile; −1.645 is the 5th. - **Growth Trajectory** — The pattern of a child's measurements across visits. Pediatricians interpret the trajectory, not a single plotted point. ## Related guides - [BMI Calculation Guide: Formula, Ranges, and Limits](https://dothecalculation.com/blog/health/bmi-calculation-guide) — Calculate adult BMI by hand, understand the standard ranges, and learn why BMI is a screening measure rather than a diagnosis. - [How to Use Do The Calculation Calculators: A Practical Step-by-Step Guide](https://dothecalculation.com/blog/site-guides/how-to-use-calculators) — Learn the fastest reliable workflow for using Do The Calculation calculators, reading results, checking formulas, and using save, print, share, and export actions correctly. ## Related calculators - [Kids BMI Percentile Calculator](https://dothecalculation.com/calculators/kids-bmi-percentile-calculator) — Find your child's BMI-for-age percentile (ages 2-13) against real CDC growth-chart reference data. - [BMI Calculator](https://dothecalculation.com/calculators/bmi-calculator) — Calculate your Body Mass Index and discover your healthy weight range instantly using height and weight for accurate results. - [Ideal Weight Calculator](https://dothecalculation.com/calculators/ideal-weight-calculator) — Find your ideal weight range based on height, gender, and body frame using trusted medical formulas for a healthy target. - [Body Fat Calculator](https://dothecalculation.com/calculators/body-fat-calculator) — Estimate your body fat percentage using common measurements like waist, neck, and height for a quick, accurate fitness assessment. - [Weight Loss Percentage Calculator](https://dothecalculation.com/calculators/weight-loss-percentage-calculator) — Calculate what percentage of your starting weight you have lost and check your weekly rate against the commonly cited gradual, sustainable range. - [3D Body Composition Calculator](https://dothecalculation.com/calculators/body-composition-3d-calculator) — Estimate body fat percentage, lean mass, skeletal muscle mass, and fat-free mass index (FFMI) using detailed body measurements. --- _This calculator is a screening reference, not a diagnosis. It uses the CDC 2000 growth chart data files for weight-for-age and stature-for-age (wtage.csv and statage.csv, National Center for Health Statistics), stored value for value, and the LMS z-score method. It covers ages 2 to 20 years. A percentile shows how one measurement compares with a reference population; a pediatrician interprets growth from the trend across several visits alongside the child's health, development and family history. Children born preterm or with conditions that affect growth may need different charts. If you are concerned about your child's growth, talk to their doctor._ --- _Source: [Do The Calculation](https://dothecalculation.com/calculators/child-growth-percentile-calculator). Quote freely with attribution and a link to this page._