# Kids BMI Percentile Calculator Find your child's BMI-for-age percentile (ages 2-13) against real CDC growth-chart reference data. --- - **Canonical URL:** https://dothecalculation.com/calculators/kids-bmi-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 --- ## Find your child's BMI percentile (ages 2-13) Enter your child's sex, age, weight, and height to see their BMI-for-age percentile against real CDC growth-chart reference data — the same method pediatricians use. - Real CDC 2000 BMI-for-age reference data, not an approximated curve - Percentile bands: underweight, healthy weight, overweight, obesity - Covers ages 2-13, the range backed by verified reference data ## Why percentile, not a raw BMI number A raw BMI number means very little for a growing child, because healthy BMI shifts constantly with age and differs between boys and girls as their bodies develop. Instead, pediatricians compare a child's BMI to the distribution of BMI values recorded for thousands of children of the same age and sex, expressed as a percentile: a 60th-percentile BMI means the child's BMI is higher than 60% of same-age, same-sex peers in the CDC reference population, not that anything is wrong. This calculator uses the CDC's 2000 BMI-for-age growth charts — the same LMS (Lambda-Mu-Sigma) reference data pediatric growth charts are built from — rather than a simplified age-band approximation. ## How the percentile is actually calculated The CDC publishes, for each age (in months) and sex, three parameters — L (a Box-Cox power for skewness), M (the median BMI), and S (a coefficient of variation) — fitted to national survey data. A child's BMI is converted to a Z-score using those parameters, then the Z-score is converted to a percentile using the standard normal distribution. This calculator linearly interpolates between the CDC's published age points for a smoother result (a method the CDC's own documentation explicitly permits) and applies the identical Z-score formula CDC uses. ## Standard percentile categories Per current CDC/AAP guidance: below the 5th percentile is categorized as Underweight, 5th to just under the 85th percentile as Healthy weight, 85th to just under the 95th as Overweight, and 95th percentile or above as Obesity. A further Severe obesity flag applies at or above 120% of the 95th-percentile BMI value for age and sex, or a BMI of 35 or higher, whichever is lower — reflecting the 2023 AAP Clinical Practice Guideline's addition of a severe-obesity tier beyond the original four CDC bands. ## Worked example: 10-year-old boy A 10-year-old boy weighing 32 kg (about 70.5 lbs) and 140 cm (about 4'7") tall has a BMI of about 16.3. Against the CDC reference data for 10-year-old boys, that works out to roughly the 44th percentile — squarely in the Healthy weight band, close to the middle of his peer distribution. ## Worked example: 8-year-old girl An 8-year-old girl weighing 25 kg (about 55 lbs) and 128 cm (about 4'2") tall has a BMI of about 15.3. Against the CDC reference data for 8-year-old girls, that works out to roughly the 38th percentile — also within the Healthy weight band, illustrating how a lower raw BMI at a younger age can land at a similar relative percentile to a different BMI at an older age. ## Important scope limitation: ages 2-13 only This calculator's underlying CDC reference dataset is verified and complete for ages 2 years through 12 years 11.5 months (24-155.5 months) for both sexes. We deliberately capped the calculator at this range rather than extrapolating or approximating data for older teenagers, since a wrong percentile for a growing child is a meaningfully worse outcome than clearly stating a limitation. If your child is 13 or older, this calculator will not return a result — check with your pediatrician, who has access to the complete CDC chart through age 20. ## What percentile does and doesn't tell you BMI percentile is a population-comparison screening tool, not a diagnosis, and it doesn't account for a child's build, muscle mass, growth stage, or family growth pattern the way a pediatrician tracking your child over multiple visits can. A single percentile reading matters less than the trend across several well-child visits — a child steadily tracking along their own percentile line is generally a better sign than any single number in isolation, even if that line sits toward either end of the distribution. ## Related calculators For adult BMI context, see the [BMI Calculator](/calculators/bmi-calculator). For a general reference weight range by height, see the [Ideal Weight Calculator](/calculators/ideal-weight-calculator). ## Frequently asked questions ### What is BMI percentile for children? It's how a child's BMI compares to the CDC reference distribution of children the same age and sex — for example, the 60th percentile means higher BMI than 60% of same-age, same-sex peers in the reference population. It's a relative comparison, not a pass/fail score. ### What age range does this calculator cover? Ages 2 years through 12 years 11 months, for both boys and girls. This range reflects the verified CDC reference data actually used in the calculation — we chose not to extrapolate beyond it rather than risk an inaccurate percentile for older children and teens. ### My child is older than 13 — where can I find their percentile? Ask your pediatrician, who has access to the complete CDC BMI-for-age charts through age 20 and can plot your child's percentile alongside their full growth history. ### What percentile is considered a healthy weight? Per CDC/AAP guidance: 5th to just under the 85th percentile is categorized as Healthy weight. Below the 5th is Underweight, 85th to just under 95th is Overweight, and 95th or above is Obesity. ### Is a high or low percentile automatically a problem? Not by itself. Percentile is a screening comparison, not a diagnosis — a pediatrician considers the trend over multiple visits, family growth patterns, and overall health, not a single percentile reading in isolation. ### What data does this calculator use? The CDC's 2000 BMI-for-age growth chart LMS reference data (the same data source used to build the printed pediatric growth charts), with linear interpolation between published age points — a method CDC's own documentation permits for finer resolution. ### What is 'severe obesity' in this calculator? A category added by the 2023 AAP Clinical Practice Guideline for BMI at or above 120% of the age/sex 95th-percentile value, or a BMI of 35 or higher (whichever threshold is lower) — a more specific flag than the standard 95th-percentile Obesity band alone. ### Should I make decisions based on this calculator alone? No. This is an educational screening tool. Always discuss your child's growth with their pediatrician, who has full growth history and clinical context this calculator doesn't have access to. ## Related concepts - **BMI-for-age percentile** — A child's BMI compared against the CDC reference distribution for their exact age (in months) and sex. - **LMS method** — The CDC's Lambda-Mu-Sigma statistical method for converting a raw measurement into an age- and sex-adjusted percentile. - **Severe obesity (120% of 95th percentile)** — A more specific high-BMI flag added by the 2023 AAP Clinical Practice Guideline, beyond the standard Obesity band. ## 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 - [Push-Up & Sit-Up Fitness Test Calculator](https://dothecalculation.com/calculators/pushup-situp-fitness-test-calculator) — Rate your push-up and sit-up counts against published age-and-sex normative tables, from Very Poor to Excellent. - [Adaptive TDEE Calculator](https://dothecalculation.com/calculators/tdee-adaptive-calculator) — Calculate your true adaptive TDEE using real-world daily calorie intake and weight trend data for more accurate results. - [Basal Body Temperature Fertility Calculator](https://dothecalculation.com/calculators/basal-body-temperature-calculator) — Check today's waking temperature against your follicular baseline for a post-ovulation thermal shift, and estimate your next period. - [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. - [BMR Calculator](https://dothecalculation.com/calculators/bmr-calculator) — Estimate your basal metabolic rate (BMR) and daily calorie needs at rest based on your age, gender, height, and weight for accurate results. - [Body Age Calculator](https://dothecalculation.com/calculators/body-age-calculator) — Estimate your body age compared to your actual age using lifestyle, fitness, and health inputs for a full wellness snapshot. --- _This calculator uses real CDC 2000 BMI-for-age reference data for ages 2-13, an explicitly limited and disclosed range. It is a screening estimate, not a diagnosis — always consult your child's pediatrician._ --- _Source: [Do The Calculation](https://dothecalculation.com/calculators/kids-bmi-percentile-calculator). Quote freely with attribution and a link to this page._