This tool is intended for use by parents, guardians, and healthcare providers — not for children to self-administer. If you've ever wondered whether your child is at a healthy weight for their age, you're not alone — it's one of the most common questions pediatricians hear at well-child visits. This calculator uses the same CDC growth chart percentile method your child's doctor relies on: rather than applying a fixed cutoff number, it compares your child's BMI against a reference population of children the same age and sex. That distinction matters enormously, because BMI for children works completely differently than it does for adults — the same raw number that's normal for a 6-year-old may be far outside the healthy range for a 16-year-old. Use these results as a starting point for a conversation with your pediatrician, who can factor in your child's full growth history, family background, and stage of development before drawing any conclusions.
BMI-for-age is a screening tool, not a diagnosis. A high or low percentile does not necessarily indicate a health problem. Only a qualified healthcare provider can interpret your child's growth in the context of their full health picture, family history, and development. Please share these results with your child's doctor.
Enter Child's Information
This result is a screening estimate only. BMI-for-age does not directly measure body fat and cannot diagnose obesity or any health condition. Growth patterns, muscle mass, bone density, and puberty stage all affect BMI. Please discuss this result with your child's pediatrician before drawing any conclusions.
How to Interpret Your Child's BMI Results
When you get a result from this calculator, the most important number isn't the raw BMI — it's the percentile. The CDC defines four weight-status categories for children based on where their BMI falls relative to other kids of the same age and sex:
| Category | Percentile Range | What It Means | Suggested Next Step |
|---|---|---|---|
| Underweight | Below the 5th percentile | BMI lower than 95% of same-age, same-sex peers | Mention at next well-child visit; track over time |
| Healthy Weight | 5th to less than 85th percentile | Within the typical range for age and sex | Continue routine monitoring at well-child visits |
| Overweight | 85th to less than 95th percentile | Higher BMI than most same-age, same-sex peers | Worth discussing at next checkup, especially if trending up |
| Obese | 95th percentile and above | Significantly higher than peers | Pediatrician evaluation recommended promptly |
A result outside the healthy range is a signal to pay attention — not a diagnosis. BMI does not directly measure body fat, and it cannot account for muscle mass, bone density, or the dramatic shifts in body composition that happen during puberty. A highly athletic child may have a high BMI percentile without any excess fat, and a sedentary child may fall within the healthy range despite poor body composition.
The CDC's percentile thresholds are also population references, not personal benchmarks. A child who has always tracked at the 88th percentile may be perfectly healthy — their doctor knows their history. A child who has jumped from the 60th to the 90th percentile in one year warrants more attention than one who has been stable at the 90th.
For comparison, adults use a completely different system with fixed cutoffs that don't adjust for age. If you're also curious about adult weight status, our adult BMI calculator applies the standard criteria used for ages 20 and older.
BMI-for-Age Percentile Chart by Age & Gender
The table below shows the approximate BMI range that corresponds to healthy weight — defined as the 5th through 85th percentile — for boys and girls at each age, based on the CDC 2000 Growth Charts. A child whose BMI falls within this range for their age and sex is considered to be at a healthy weight by CDC standards.
| Age | Boys — Healthy BMI Range (5th–85th percentile) |
Girls — Healthy BMI Range (5th–85th percentile) |
|---|---|---|
| 2 years | 14.4 – 18.2 | 14.2 – 18.0 |
| 3 years | 14.0 – 17.7 | 13.8 – 17.5 |
| 4 years | 13.7 – 17.2 | 13.5 – 17.0 |
| 5 years | 13.7 – 17.1 | 13.5 – 17.0 |
| 6 years | 13.7 – 17.1 | 13.5 – 17.1 |
| 7 years | 13.8 – 17.5 | 13.6 – 17.8 |
| 8 years | 13.9 – 18.0 | 13.8 – 18.9 |
| 9 years | 14.1 – 18.9 | 14.0 – 20.4 |
| 10 years | 14.4 – 19.8 | 14.3 – 22.1 |
| 11 years | 14.8 – 21.0 | 14.7 – 23.4 |
| 12 years | 15.3 – 22.1 | 15.2 – 24.7 |
| 13 years | 16.0 – 23.3 | 15.8 – 25.9 |
| 14 years | 16.8 – 24.4 | 16.4 – 27.0 |
| 15 years | 17.5 – 25.2 | 17.1 – 28.0 |
| 16 years | 18.0 – 25.9 | 17.7 – 28.5 |
| 17 years | 18.5 – 26.5 | 18.2 – 29.1 |
| 18 years | 18.9 – 27.3 | 18.6 – 29.5 |
| 19 years | 19.2 – 27.8 | 18.7 – 30.0 |
Values are approximate, based on CDC 2000 Growth Charts (LMS percentile reference data). Ranges represent the 5th–85th percentile boundary for each sex. Source: CDC. "About Child & Teen BMI." cdc.gov/healthyweight.
Notice how the healthy BMI range for girls begins widening significantly around age 9–10, earlier than for boys. This reflects the typical earlier onset of puberty in girls, which causes a normal upward shift in BMI distributions as body fat naturally increases during sexual development. The percentile system accounts for this — which is why the same raw BMI number means something quite different at age 10 versus age 15.
If you're tracking your family's nutrition alongside weight, our calorie calculator and ideal weight calculator may also be useful reference tools for adult household members.
Toddlers vs. Teens: How Age Changes BMI Interpretation
One of the most confusing aspects of childhood BMI is that the healthy range isn't fixed — it shifts continuously with age, and the shift isn't even linear. A 5-year-old and a 12-year-old with identical raw BMI values will fall into completely different percentile categories, and rightly so. Young children have lower body fat percentages relative to their size than adolescents do, and they carry that fat differently. Boys and girls also diverge substantially in their growth patterns from early puberty onward. The CDC percentile system captures all of this by comparing each child only to peers of the same age and sex, not to a single universal standard.
Toddlers between ages 2 and 5 often have BMIs that look slightly elevated compared to the adult standard, and some still carry a bit of the rounded proportions common in infancy. This is developmentally normal. During the preschool years, most children naturally slim down as they become more physically active and as height accelerates relative to weight — a phase pediatricians sometimes call "adiposity rebound." The age at which this natural slimming bottoms out (typically around 5–6 years) and BMI begins gradually rising again is itself a health predictor: children who experience adiposity rebound earlier than average have a somewhat higher risk of elevated BMI in later childhood, which is one reason pediatricians track growth trajectories rather than single data points.
As children enter the tween and teen years — roughly ages 9 to 14 — puberty introduces the most dramatic changes in how BMI should be read. Girls typically begin puberty 1–2 years earlier than boys, and the hormonal changes involved produce a normal increase in body fat that is already built into the CDC reference charts. This is why the 85th percentile BMI threshold for a 14-year-old girl (around 27.0) is notably higher than for a 14-year-old boy (around 24.4). A teenager with a BMI that seems high by adult standards may sit comfortably within the healthy percentile range for their specific age and sex. This is precisely why the raw BMI number, viewed without the percentile context, tells you very little about a young person's actual health.
Frequently Asked Questions
What is a healthy BMI for a child?
Unlike adult BMI, which uses fixed cutoff numbers regardless of age, a healthy BMI for a child depends entirely on their age and sex. The CDC defines healthy weight as a BMI-for-age between the 5th and 85th percentile. A BMI of 16.5 might be perfectly healthy for a 7-year-old boy near the 50th percentile, while that same number might fall in the underweight range for a 14-year-old. Pediatricians always interpret BMI in the context of a child's full growth chart over time, not as a standalone number.
How is BMI calculated differently for children vs. adults?
The formula is identical for everyone: weight in kilograms divided by height in meters squared (kg/m²). The difference is entirely in how the result is interpreted. For adults, fixed cutoffs apply regardless of age — under 18.5 is underweight, 18.5–24.9 is healthy, and so on. For children ages 2–19, the raw BMI is compared to CDC age- and sex-specific growth chart percentiles, because body composition changes continuously through childhood and puberty. A child at the 50th percentile has a higher BMI than 50% of same-age, same-sex peers — which is considered healthy. Our adult BMI calculator applies the standard adult cutoffs for ages 20 and above.
What BMI percentile is considered overweight for kids?
According to the CDC, a child is classified as overweight when their BMI-for-age falls at or above the 85th percentile and below the 95th percentile. A child at or above the 95th percentile is classified as obese. These thresholds were established based on large U.S. population surveys and health outcomes research. They are screening categories, not diagnoses — muscle mass, bone density, puberty stage, and the trajectory of BMI over time all affect how a healthcare provider interprets these categories for an individual child.
What is a normal BMI for a 10-year-old?
A normal (healthy weight) BMI for a 10-year-old boy typically falls between approximately 14.4 and 19.8, while for a 10-year-old girl the healthy range is approximately 14.3 to 22.1. These represent the 5th through 85th CDC percentile for each sex. Keep in mind that BMI is one data point among many — how a child's measurements trend across multiple well-child visits, physical activity level, diet quality, and overall health picture matter far more than any single reading.
How do I calculate my teenager's BMI?
The BMI formula for a teenager is the same as for anyone: weight in kilograms divided by height in meters squared. Using pounds and inches: BMI = (weight in lbs × 703) ÷ (height in inches)². However, the raw BMI number only becomes meaningful when compared to CDC age- and sex-specific percentile tables — because a BMI of 22 means very different things for a 13-year-old versus a 17-year-old. The calculator on this page handles that automatically. Just enter your teen's age, sex, height, and weight, and it will calculate both the raw BMI and the CDC percentile using the LMS reference method.
Is BMI accurate for toddlers?
BMI-for-age is a valid screening tool for children age 2 and older, but it has more limitations for toddlers than for older children. Toddlers grow rapidly and unevenly — a child may appear to have a high BMI during a growth spurt and then slim down naturally as height catches up over the next few months. The CDC BMI-for-age charts begin at 24 months (2 years) because weight-for-length is the more appropriate growth measure before that age. For toddlers, pediatricians typically focus on growth velocity — how measurements change over time — rather than any single percentile reading. Always discuss toddler growth concerns with your child's doctor.
What is the CDC BMI-for-age percentile chart?
The CDC BMI-for-age percentile chart is a standardized growth reference tool published by the Centers for Disease Control and Prevention, derived from large U.S. population surveys — the National Health Examination Survey (NHES) and National Health and Nutrition Examination Survey (NHANES) data collected between 1963 and 1994. It provides smooth reference curves showing the statistical distribution of BMI values by age and sex for children ages 2 through 19. The 2000 CDC Growth Charts use a statistical technique called the LMS method, which accounts for the natural skewness of BMI distributions, to generate accurate percentile curves. Pediatricians use these charts at well-child visits to track how a child's growth compares to the reference population over time.
What BMI percentile is underweight for children?
The CDC defines underweight as a BMI-for-age below the 5th percentile, meaning the child's BMI is lower than that of 95% of children of the same age and sex in the reference population. Underweight can result from inadequate caloric intake, chronic illness, metabolic conditions, or simply a naturally lean body type. A single low percentile reading is not automatically alarming, especially if the child has always tracked at a lower percentile and is growing steadily. However, if your child consistently falls below the 5th percentile, or if their percentile drops noticeably across multiple well-child visits, that is worth discussing with your pediatrician.
How do I calculate my child's BMI in metric?
Measure your child's height in meters and weight in kilograms, then apply the formula: BMI = weight (kg) ÷ height (m)². For example, a child who is 1.30 m tall and weighs 30 kg has a BMI of 30 ÷ (1.30 × 1.30) = 30 ÷ 1.69 ≈ 17.8. To find out what CDC percentile that corresponds to for your child's specific age and sex, use the calculator above with the Metric (kg / cm) option selected — it will convert the raw BMI to a percentile automatically using the LMS reference data.
What is a normal BMI for a teenager?
A normal (healthy weight) BMI for a teenager varies by age and sex. For a 15-year-old boy, the healthy range (5th–85th CDC percentile) is approximately 17.5–25.2; for a 15-year-old girl it's approximately 17.1–28.0. For a 17-year-old boy the range is roughly 18.5–26.5, and for a 17-year-old girl approximately 18.2–29.1. Because teenagers are still growing and puberty causes significant changes in body composition, a raw BMI number tells you far less than the CDC percentile for their specific age and sex. See the full age-by-age table in the section above, or use the calculator to get a personalized result for your teen.
What is a healthy BMI for a toddler (ages 2–5)?
For toddlers aged 2–5, the healthy weight range (5th–85th CDC percentile) falls roughly between BMI 13.5 and 17.5, depending on the child's exact age and sex. At age 2, the healthy range for boys is approximately 14.4–18.2 and for girls 14.2–18.0. By age 5, those ranges shift slightly to 13.7–17.1 for boys and 13.5–17.0 for girls, reflecting the natural slimming that typically happens during the preschool years. Toddlers grow unevenly — a BMI that looks slightly elevated at one visit may be completely normal a few months later after a height growth spurt. If you have concerns, your child's pediatrician can plot the measurement on a growth chart and put it in the context of their overall growth pattern.
What should I do if my child's BMI percentile is too high?
A BMI at or above the 85th percentile is a signal to pay attention — not to panic. Bring it up at your child's next well-child visit so the pediatrician can review the full growth history. They can determine whether the reading reflects true excess body fat or factors like a growth spurt or naturally higher muscle mass. If action is needed, the approach for children differs from adults: strict caloric restriction is rarely recommended for growing kids. Instead, the focus is typically on slowing weight gain while allowing height to continue growing — through whole-food meals, fewer sugary drinks, more daily active play, and less screen time. Avoid singling out a child for their weight; research consistently shows that weight-focused conversations with children can contribute to disordered eating. Frame any changes as family habits that benefit everyone.
Can boys and girls both use this BMI calculator?
Yes — this calculator works for both boys and girls ages 2 through 19. Sex is a required input because the CDC growth charts are sex-specific: boys and girls have different average BMI distributions at every age, and those differences grow larger during puberty when hormonal changes affect body fat differently by sex. Selecting the correct sex ensures your child's BMI is compared against the appropriate reference group. For children whose gender identity differs from their sex assigned at birth, most clinical guidelines currently recommend using biological sex for CDC BMI-for-age calculations since the reference charts are based on biological sex data — your child's pediatrician can advise on interpretation.
What is a normal BMI for an 8-year-old?
For an 8-year-old boy, a healthy weight falls between approximately BMI 13.9 and 18.0 (5th–85th CDC percentile). For an 8-year-old girl, the healthy range is approximately 13.8–18.9 — slightly wider because girls begin accumulating a bit more body fat in the years approaching puberty. If your 8-year-old's result falls outside these ranges, use the calculator above to get a precise percentile, then bring it to your pediatrician at the next visit. A single reading outside the healthy zone is not a diagnosis — what matters most is whether that reading is new or has been consistent, and how the child is growing overall over multiple visits.
What to Do If Your Child's BMI Result Is High or Low
If the result shows Overweight or Obese (85th percentile or above)
Start by bringing the result to your child's pediatrician — don't make changes to diet or exercise based on a single calculator reading alone. The pediatrician can review the growth chart over time, check whether the percentile has shifted recently, and rule out factors like a growth spurt, high muscle mass, or a naturally larger frame before deciding whether any action is needed.
When the doctor agrees that weight is a concern, the approach for children is different from adults. Strict caloric restriction is rarely recommended for growing kids, as it can interfere with normal development. Instead, the focus is typically on slowing weight gain while allowing height to continue growing — through gradual changes like replacing processed snacks with whole foods, reducing sugary drinks, increasing daily physical activity, and cutting leisure screen time. A pediatric dietitian can help tailor a realistic plan. At home, avoid making a child feel ashamed or singled out; research consistently shows that weight-focused conversations with children can contribute to disordered eating. Frame any lifestyle changes as family decisions that benefit everyone.
If the result shows Underweight (below the 5th percentile)
A single low reading is not necessarily cause for alarm, especially if the child has always been naturally lean, is growing steadily in height, has good energy, and eats reasonably well. Mention it at the next pediatric visit so the doctor can review the complete growth trajectory and check for any underlying causes — insufficient caloric intake, dietary restrictions, food allergies, gastrointestinal issues, or other medical factors. If the child has dropped significantly in percentile since a prior visit, or is showing signs like fatigue, hair thinning, or consistently poor appetite, bring it up sooner rather than waiting for the next routine appointment.
If the result is in the Healthy Weight range (5th–85th percentile)
No specific action is needed beyond continuing routine well-child visits. Healthy weight in childhood is best maintained through habits rather than monitoring: daily physical activity, balanced meals that emphasize whole foods, adequate sleep, and limited ultra-processed foods and sugary drinks. These habits, established early, are the most durable predictors of a healthy weight trajectory through adolescence and into adulthood.
When to Talk to Your Pediatrician
This calculator is a helpful starting point — not a finish line. A pediatrician who knows your child is always in the best position to put a BMI result in context. They can look at how your child's percentile has trended over years of visits, consider growth velocity, ask about diet and activity habits, and factor in family health history. A result that looks concerning in isolation may be perfectly appropriate for your child, and vice versa.
That said, here are situations where it's especially worth bringing up BMI at your next visit: if your child's result falls below the 5th or above the 85th percentile for the first time; if the percentile has shifted noticeably since the last measurement; if your child has expressed concern or self-consciousness about their weight; or if you've noticed changes in eating habits, energy level, or growth pace.
Most importantly, try to frame conversations at home around health and how the body feels — not numbers. Children hear more than we realize, and the way we talk about weight, whether ours or theirs, shapes their relationship with food and their own body for years to come. A pediatrician can help you approach those conversations in a way that is right for your child's age and temperament.
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Sources & Methodology
Formula: BMI-for-age percentile using the CDC LMS (Lambda-Mu-Sigma / Box-Cox power transformation) method applied to the CDC 2000 Growth Charts reference population.
Interpretation (CDC classification): Underweight <5th percentile · Healthy Weight 5th–84th percentile · Overweight 85th–94th percentile · Obese ≥95th percentile.
Sources: Centers for Disease Control and Prevention (CDC). CDC Growth Charts, United States (2000). National Center for Health Statistics. BMI-for-age percentile is a screening tool only — it does not constitute a diagnosis. All growth concerns should be discussed with the child's pediatrician.
Last reviewed: June 2026