2026-09-15 10 min

Teen BMI Calculator

Compute BMI-for-age percentile and z-score for teens ages 13–19 on CDC growth charts, with weight-status category, healthy weight band, and muscle-vs-fat guidance for young athletes.

Calculator

Age (13–19)

yrs

Male Female

Height

≈ 3'11"–7'7"

Weight

lbs

55–550 lbs

Results update live as you type

Status:62.7th percentileHealthy WeightHealthy 16.6–22.2 BMI

Teen BMI Results

BMI-for-Age Percentile62.7th

Weight StatusHealthy Weight

BMI20.7 kg/m²

z-Score+0.32 SD

Healthy Weight Range106.0–141.9 lbs

Detailed Metrics

Metric	Value	Reference
BMI	20.7 kg/m²	Quetelet formula
BMI-for-Age Percentile	62.7th	CDC same-age, same-sex
z-Score	+0.32 SD	LMS transform
Healthy BMI Band (5th–85th)	16.6–22.2 kg/m²	this age + sex
Healthy Weight Range	106.0–141.9 lbs	48.1–64.4 kg
Obesity Threshold (95th)	BMI 23.6 kg/m²	screening line

Recommendations

▸Healthy weight (63th percentile) — support daily movement, 8–10 hours of sleep, and regular meals
▸Yearly checkups are enough; trajectory over a year is what counts, not monthly weigh-ins
▸Sudden percentile jumps without lifestyle changes deserve a checkup — medications, sleep loss, and endocrine conditions move weight too

Results

Optimal

BMI-for-Age Percentile

62.7th

Ranked against CDC same-age, same-sex peers

Body Mass Index

20.7kg/m²

Same Quetelet formula as adults — the percentile does the interpreting

Weight Status

Healthy Weight

Between the 5th and 85th percentile — the healthy range for children and teens.

z-Score

+0.32SD

Standard deviations from the age–sex median (LMS method)

Healthy BMI Band

16.6–22.2kg/m²

5th–85th percentile BMI range at this exact age and sex

Healthy Weight Range

48.1–64.4kg

Weight span for the 5th–85th band at this height

Teen BMI is a screening rank, not a diagnosis — puberty timing and training load can shift it substantially. If your teen trains seriously, cross-check with waist-to-height ratio, and keep all weight talk supportive.

Visualizations

Weight vs Healthy Range

48.1kgHealthy Min

59.9kgTeen

64.4kgHealthy Max

BMI-for-Age Percentile (0–100)

Percentile62.7th

Formula

Teen assessment reuses the child LMS machinery with adolescent reference curves: raw BMI is standardized against the CDC parameters for the exact age and sex, then ranked as a percentile. Adult cutoffs are never consulted before age 20.

BMI = W(kg) ÷ H(m)², then z = ((BMI / M)^L − 1) / (L × S)

Alternative Form

Percentile = Φ(z) × 100 (standard normal CDF)

Variables

Symbol	Name	Unit	Description
BMI	Body Mass Index	kg/m²	Weight relative to height squared; the raw input to the percentile machinery
W	Weight	kg (or lbs)	Body weight; pounds convert at 2.20462 per kg
H	Height	m (or in)	Standing height, barefoot, in meters (metric) or inches (US)
L, M, S	LMS parameters	—	CDC Box-Cox power, median, and spread for the exact teen age and sex
z	z-score	SD	Standardized BMI; the percentile is Φ(z) × 100
Band	Healthy band	kg/m²	5th–85th percentile BMI range at this age and sex

Explanation

Because puberty moves the median (M) and spread (S) of BMI quickly, the same raw BMI maps to very different percentiles at 13 versus 18 — and for boys versus girls. The LMS transform absorbs all of that: it asks how unusual this BMI is among true peers.

Derivation

The CDC 2000 charts fitted LMS curves through adolescence from NHANES data, capturing the pubertal BMI rise in both sexes. The 85th/95th screening lines were carried over from pediatric consensus so childhood tracking continues seamlessly into the teen years.

Step-by-Step Calculation

Follow each step to understand how the result is calculated from your inputs.

Step 1

Convert height to a single unit.

Total in = ft × 12 + in

Height:67.0 in

Intermediate: from 5'7"

Result: Height = 67.0 in

Step 2

Compute BMI the usual way.

BMI = 703 × lbs ÷ in²

Weight:132.0 lbs

Intermediate: 703 × 132.0 ÷ 4489.0

Result: BMI = 20.7 kg/m²

Step 3

Look up the CDC LMS parameters for this adolescent age and sex.

LMS table: CDC 2000, interpolated

Age:15.0 yrs

Sex:male

L:0.590

M:19.98

S:0.106

Intermediate: L = 0.590, M = 19.98, S = 0.106

Result: Reference median BMI 20.0 at age 15.0

Step 4

Convert BMI to a z-score with the LMS transform.

z = ((BMI / M)^L − 1) / (L × S)

BMI:20.7

M:19.98

Intermediate: ((20.67 / 19.98)^0.590 − 1) / (0.590 × 0.106)

Result: z ≈ +0.32

Step 5

Convert the z-score to a percentile and classify.

Percentile bands: 5 / 85 / 95

z:+0.32

Intermediate: Placed against the 5th / 85th / 95th lines

Result: 62.7th percentile — Healthy Weight

Step 6

Report the healthy band and check the athlete confound.

Band = 5th–85th BMI; WHtR = waist ÷ height ≤ 0.5

Band:16.6–22.2 BMI

Intermediate: 5th/85th percentile weights at 170.2 cm

Result: 48.1–64.4 kg healthy at this height

Final Answer

62.7th

Worked Examples

See how the calculator works with different scenarios.

Scenario

A 15-year-old boy, 170 cm and 60 kg, measured during a sports physical.

Inputs

Age:15 years

Sex:Male

Height:170 cm

Weight:60 kg

Calculation

BMI = 60 ÷ (1.70)² = 60 ÷ 2.89 = 20.8; LMS z ≈ +0.37

Result

BMI 20.8 kg/m² | ~64th percentile (Healthy Weight) | z ≈ +0.37

Interpretation

At the 64th percentile he is mid-healthy. The agreement with adult “healthy” here is luck — the same comparison fails badly at most teen BMIs, so always use the percentile.

Understanding Your Result

Your Result: BMI-for-Age Percentile: 62.7th

Typical range: Healthy teens track anywhere in the 5th–85th band along their own curve. A dip around peak height velocity (11–13 in girls, 13–15 in boys) is usually timing, not thinness.

What This Means

The percentile ranks the teen’s BMI against CDC reference peers of the same age and sex: under 5th is underweight, 5th–85th healthy, 85th–95th overweight, 95th+ obese.

Why It Matters

Puberty is the hardest window to interpret BMI — and where misinterpretation does the most harm. The percentile adjusts for growth timing automatically, and its trajectory separates real change from spurt timing.

Professional Interpretation

Clinicians read teen percentiles with puberty stage, training load, and z-score change in mind. For athletic teens they cross-check waist-to-height ratio before accepting an “overweight” label; for rapid percentile crossings they look for causes including medications and sleep.

Muscle vs fat: the teen athlete problem

Resistance training, football, wrestling, rowing, and gymnastics build lean mass that BMI counts identically to fat. The practical screen is waist-to-height ratio: divide waist by height in the same units and treat 0.5 as the flag line.

Why z-scores beat percentiles at the top

A move from z +2.0 to +1.6 is big clinical progress that barely moves the percentile (98th to 95th). Tracking z change keeps motivation honest during long programs.

Recommendations

•Percentile 5th–85th: support daily activity, 8–10 hours of sleep, and regular meals
•Percentile 85th–95th: review habits plus body composition if the teen trains
•Percentile 95th+: pursue a pediatrician-guided, habits-based plan — no crash diets
•Percentile under 5th: rule out under-fueling, especially in endurance athletes
•Recheck yearly (or twice-yearly with a clinician); avoid weekly home weigh-ins

Educational Content

Introduction

The teen years are the hardest window to interpret BMI — and the window where misinterpretation does the most harm. This calculator ranks teens 13–19 against CDC adolescent reference curves with full puberty-aware context.

Concept Explanation

Raw BMI is standardized with CDC LMS parameters for the exact age and sex into a z-score, then ranked as a percentile. Peak height velocity, sex-specific fat and muscle deposition, and training load all sit behind the number — the percentile plus its trajectory sorts timing from real change.

Applications

▸Yearly well-visit screening through adolescence

▸Sports physicals that need muscle-vs-fat context

▸Tracking percentile trajectories across puberty

▸Distinguishing growth-spurt dips from real thinness

▸Guiding family habits plans without disordered-eating risk

▸Flagging rapid percentile crossings for clinical follow-up

Benefits

•Puberty-aware: compares against true same-age, same-sex peers
•Athlete flags: prompts waist-to-height cross-checks for trainers
•z-score tracking shows progress percentiles hide
•Spurt-timing guidance prevents overreaction to dips
•Supportive framing keeps teen weight talk behavior-focused

Limitations

•Cannot see composition — lean mass reads like fat
•No puberty-stage (Tanner) input for borderline cases
•Single readings are noisy around growth spurts
•Screening flags only — diagnosis belongs with a pediatrician

Best Practices

•Enter age precisely (decimals allowed) — medians move fast in teens
•Always select the correct sex; tables diverge sharply after puberty onset
•Read 2–3 readings across a year, not single points
•Cross-check athletic “overweight” with waist-to-height ratio ≤ 0.5
•Keep weight talk supportive; teen years are peak disordered-eating risk

Common Misconceptions

Myth: Adult cutoffs approximately work for older teens.

Truth: A 16-year-old girl at BMI 26.3 is ~99th percentile (obese band), yet adult rules say merely “overweight.” The verdict flips without the percentile.

Myth: A muscular teen labelled overweight should cut weight.

Truth: Football, wrestling, and lifting build BMI-counted lean tissue. Check the waistline and body-fat estimate first — cutting can harm performance and growth.

Myth: Frequent weighing keeps teens accountable.

Truth: Weekly weigh-ins through puberty mostly track spurts and water. Yearly percentile plots show the real trajectory with far less anxiety.

Practical Tips

•Always use the percentile, never adult cutoffs — a teen BMI of 26 can be overweight or obese by age and sex
•Enter age precisely (decimals allowed): the reference median moves quickly through the teen years
•Select the correct sex — male and female LMS tables diverge sharply after puberty onset
•Read the trajectory, not the point: 2–3 readings across a year reveal spurt timing vs real change
•For athletic teens, cross-check with waist-to-height ratio (≤ 0.5) before accepting an “overweight” label
•Target habits, not scale numbers: daily movement, water over soda, regular meals, 8–10 hours of sleep
•Strength training 2–3x weekly builds the muscle that keeps teen BMI honest
•Keep weight talk supportive and behavior-focused through the peak disordered-eating-risk years

Common Mistakes

Applying adult cutoffs to teens

A 16-year-old girl at BMI 26.3 is ~99th percentile (obese band), yet adult rules would say merely “overweight.” This calculator never reports adult categories for teens.

Ignoring puberty timing

Early and late maturers of the same age have different expected composition. Note developmental context with the pediatrician for borderline cases.

Calling muscular teen athletes overweight

Training builds BMI-counted mass that is lean tissue. Before any “overweight” conversation with a training teen, check the waistline and ideally a body-fat estimate.

Crash-dieting during growth

Severe restriction can impair bone accrual, growth, and hormones. Teens above the 85th percentile do best with habits-based, family-supported plans — slow and steady.

Over-monitoring the scale

Weekly home weigh-ins through puberty mostly track spurts and water. Yearly (or twice-yearly) percentile plots show the real trajectory with far less anxiety.

Comparing teens to each other

Same-age teens can be years apart developmentally. The percentile already compares correctly against the national reference — peer comparison adds noise and shame.

Assumptions

This calculator makes the following assumptions to provide estimates:

Ages 13–19 only: This page covers adolescence; the same CDC reference extends down to 2 (see Child BMI Calculator) and hands off to adult cutoffs at 20.

CDC 2000 reference population: Percentiles rank against the CDC growth-chart reference cohort; clinician judgment applies for populations with different growth patterns.

LMS interpolation: Parameters between yearly CDC anchors are linearly interpolated, matching standard clinical calculator practice.

Developmental context assumed: Results are pure BMI-for-age ranks; puberty stage, training load, medications, and conditions are not inputs and can shift interpretation.

Limitations

Be aware of these limitations when using this calculator:

Muscle blindness: The teen athlete problem: lean mass from training inflates BMI identically to fat. Composition-agnostic by design.

No puberty-stage input: Tanner stage strongly affects expected composition but is not collected here — borderline percentiles need clinical context.

Single-point noise: Spurts, hydration, and measurement error move single readings; trajectories across visits carry the signal.

Screening, not diagnosis: The 85th/95th lines are screening flags. Diagnosis and management belong with a pediatrician, ideally tracking z-score change.

Frequently Asked Questions

Answers to common questions about this calculator.

How is teen BMI different from adult BMI?

Teens 13–19 are assessed with CDC BMI-for-age percentiles, not fixed adult cutoffs. Under the 5th percentile is underweight, 5th–85th is healthy, 85th–95th is overweight, and 95th+ is obese — always ranked against same-age, same-sex peers. Adult cutoffs only begin at age 20.

Why does puberty make BMI tricky?

Puberty reshuffles everything BMI measures: growth spurts add height fast (temporarily lowering BMI), then muscle and fat fill in. Girls gain proportionally more fat and boys more muscle, on different schedules. Two teens with identical BMI can be at very different developmental stages, which is why the percentile — and its trajectory — matters more than the number.

My teen is muscular from sports — is BMI misleading?

Very possibly. Strength-trained teens, football linemen, wrestlers, and gymnasts routinely land in the 85th–95th+ range on lean mass alone. If your teen trains seriously and looks lean, check waist-to-height ratio (keep at or below 0.5) and ask about body-fat testing rather than trusting the percentile alone.

What is a BMI percentile for a teen?

The share of same-age, same-sex teens in the CDC reference with a lower BMI. A 15-year-old boy at the 64th percentile has a higher BMI than 64% of 15-year-old boys. It is a peer ranking that automatically adjusts for where they are in growth.

What is the z-score in the results?

The z-score is the statistical engine behind the percentile, from the LMS method: standard deviations from the age–sex median. z = 0 is exactly average (50th percentile). Clinicians track z-scores over time because percentiles compress near the extremes.

Should a teenager diet to lose weight?

Restrictive dieting is risky during growth and linked to disordered eating. For teens above the 85th percentile, evidence-based guidance focuses on habits: daily activity, sugary-drink reduction, regular meals, 8–10 hours of sleep, and less recreational screen time — ideally with pediatrician or dietitian support, never crash diets.

How do growth spurts affect the percentile?

Height spurts typically precede weight fill-in, so BMI percentile often dips just before a spurt and rebounds after. A single-point drop or jump around a visible growth spurt is usually normal timing — the pattern across 2–3 visits tells the real story.

Do boys and girls use different teen charts?

Yes — separate CDC LMS tables, because male and female composition diverges sharply in puberty (muscle vs fat patterning, timing of peak growth). This calculator applies the correct table from the sex you select.

What does the 90th percentile mean for a 16-year-old?

Their BMI exceeds 90% of same-age, same-sex peers, landing in the overweight band (85th–95th). It is a prompt to review activity, sugary drinks, sleep, and screen habits — plus body composition if they train — not a diagnosis.

How often should teens check BMI?

Yearly at routine checkups is enough for most teens, or every 6 months if actively working on habits with a clinician. Monthly home tracking adds noise and can feed unhealthy fixation — trajectory over a year is what counts.

When does a teen switch to adult BMI?

At age 20. The CDC reference runs to age 20, and the WHO adult cutoffs (18.5/25/30) take over there. A 19-year-old at the 80th percentile and a 20-year-old at BMI 24 are both simply “healthy” under their respective systems.

Can medications or conditions affect teen BMI?

Yes — some medications (including certain contraceptives, antidepressants, and steroids) and conditions (hypothyroidism, PCOS) shift weight. If a percentile jumps without lifestyle changes, mention medications and symptoms to the pediatrician.

Related Calculators

Explore more calculators related to this topic.

Related Guides

Deepen your understanding with these educational resources.

Understanding Your Teen’s BMI Percentile

From first reading to a habits plan your family can follow.

Puberty, Spurts, and Weight

Timing effects every parent of a teen should know.

Fueling Young Athletes

Muscle, performance, and why the scale misleads.

Sleep, Screens, and Teen Weight

The two biggest levers hiding in plain sight.

Glossary

Technical terms used in mortgage calculations explained in plain language.

BMI-for-Age Percentile: A teen’s BMI ranked 0–100 against CDC reference peers of the same age and sex. The headline output of this calculator.
LMS Method: Box-Cox transform (L = skew, M = median, S = spread) converting skewed BMI distributions into z-scores behind CDC charts.
z-Score: Standard deviations from the age–sex median; clinicians track z change because percentiles saturate near the top.
Growth Spurt: Peak height velocity (roughly 11–13 in girls, 13–15 in boys) that temporarily depresses BMI before weight catches up.
Peak Height Velocity: The fastest growth phase of puberty; percentile dips around it are usually timing, not thinness.
Waist-to-Height Ratio: Waist divided by height; ≤ 0.5 is the cross-check exposing muscle-vs-fat misclassification in athletic teens.
Overweight (Teen): BMI-for-age from the 85th up to the 95th percentile — a screening band, not a diagnosis.
Obese (Teen): BMI-for-age at or above the 95th percentile — prompts clinician-guided, habits-based management.
Percentile Crossing: Moving up or down across percentile lines between visits; rapid upward crossing is the pattern pediatricians watch most.
CDC Growth Charts: The CDC 2000 reference curves (LMS parameters by age and sex) against which child and teen BMI is ranked.

Authoritative References

Trusted sources and standards referenced by this calculator.

CDC — About BMI for Children and Teens CDC — Child & Teen BMI Growth Charts WHO — Growth Reference for Ages 5–19 NIH — Overweight and Obesity Harvard T.H. Chan — Healthy Weight American Heart Association — BMI in Adults Mayo Clinic — Childhood Obesity

Applicable Standards

CDC BMI-for-age percentiles (5th / 85th / 95th screening lines)CDC 2000 Growth Charts LMS parameters (ages 2–20)WHO Growth Reference for ages 5–19

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Page Information

Last Updated:

2026-09-15

Version:

2.0.0

References:

License:

Free to use for educational and professional purposes.