BMI Calculator: Accurate BMI, Categories, and Health Context
Calculate BMI instantly using metric or US units, see adult BMI categories (WHO/CDC), Asian cutoffs, and waist/central obesity context; learn BMI limits for athletes and children with evidence‑based guidance
BMI Calculator — Calculate Body Mass Index, Weight Status, and Health Context |
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Get fast, accurate BMI results from height and weight, along with the standard adult categories and health context to understand weight status and next steps.
Choose metric or US units, calculate instantly, and learn when to consider waist measurements or other indicators beyond BMI for a more complete picture of health.
What this page offers
Instant BMI calculation with metric and US formulas, including the 703 factor for imperial inputs, plus normal weight ranges for quick interpretation.
Adult BMI categories from authoritative public health sources, including WHO/CDC standards and notes on lower cutoffs commonly applied in many Asian populations.
Context on BMI limitations (muscularity, body composition, age, sex), and guidance to consider waist measures and central adiposity risk in addition to BMI.
Pediatric BMI percentile context and a clear recommendation to use age‑/sex‑adjusted charts for children and teens rather than adult thresholds.
Providing clinically consistent categories with clear caveats helps users interpret BMI appropriately while meeting the intent behind high‑volume BMI queries.
How BMI is calculated
BMI is the ratio of weight to height squared: BMI=weight (kg)height (m)2, which classifies adult weight status in standardized ranges for population screening.
For US units, BMI=weight (lb)height (in)2×703, enabling the same index with common imperial measurements used in many calculators and health portals.
These equations are globally standard for adults and are the foundation of BMI calculators and surveillance statistics in public health.
Adult BMI categories
For most adults, WHO/CDC‑aligned categories are used in clinical guidance and public health reporting, with obesity further subclassified into classes I–III for risk stratification.
| Category | BMI (kg/m²) | Source |
|---|---|---|
| Underweight | < 18.5 | WHO/CDC |
| Healthy (Normal) | 18.5–24.9 | WHO/CDC |
| Overweight | 25.0–29.9 | WHO/CDC |
| Obesity (Class I) | 30.0–34.9 | CDC |
| Obesity (Class II) | 35.0–39.9 | CDC |
| Obesity (Class III) | ≥ 40.0 | CDC |
Many Asian and South Asian populations use lower BMI cutoffs for public health risk due to higher metabolic risk at lower BMI, commonly recognizing overweight from 23 and obesity from 25 in population guidance contexts.
These population‑specific thresholds aim to capture earlier risk, and users in such regions may see BMI messaging adjusted accordingly by local health authorities.
Pediatric BMI (brief)
Children and teens require age‑ and sex‑specific percentiles rather than adult cutoffs because growth and body composition vary across development.
For example, underweight is <5th percentile, healthy weight is 5th–<85th, overweight is 85th–<95th, and obesity is ≥95th percentile on CDC charts for ages 2–20.
BMI should be interpreted within pediatric growth assessment, not adult ranges, to avoid misclassification in growing individuals.
Waist and central adiposity context
BMI does not capture fat distribution, so waist circumference and related measures help identify central (visceral) fat associated with cardiometabolic risk.
Public health guidance often flags increased risk at waist sizes >102 cm (40 in) for men and >88 cm (35 in) for women, complementing BMI categories in risk assessment.
Waist metrics are correlated with type 2 diabetes, dyslipidemia, hypertension, and CVD risk, often refining risk understanding beyond BMI alone.
Clinicians frequently assess waist along with BMI to guide prevention and counseling where central adiposity is elevated.
Limitations and when BMI misleads
BMI is a simple screening tool that does not differentiate muscle from fat, so highly muscular individuals can be misclassified as overweight or obese despite low body fat.
Age, sex, ethnicity, and body composition influence risk at a given BMI, and additional measures like waist and clinical evaluation are recommended for a fuller assessment.
Health organizations emphasize that BMI is not a diagnostic of health or body fatness by itself, and should be paired with other indicators for personalized guidance.
How to use the calculator
Select unit system (metric or US), enter height and weight, and compute BMI instantly with the correct formula for the given units.
Review adult category mapping and consider population‑specific thresholds if relevant; for children/teens, consult growth‑chart percentiles rather than adult cutoffs.
If BMI is borderline or high, measure waist and review thresholds, as central adiposity can elevate risk even at modest BMI values.
Placing the widget high on the page with clear labels and instant results supports task completion and aligns with Google’s usability and SEO starter guidance.
Worked examples
Metric example: 82 kg and 1.75 m gives BMI=821.752≈26.8, which maps to overweight in adult standards.
US example: 184 lb and 5 ft 10 in (70 in) gives BMI=184702×703≈26.4, also overweight in adult standards.
Examples help visitors verify the calculator and interpret results against familiar thresholds from authoritative sources.
Who this helps
General health: screening for underweight, healthy, overweight, or obesity status to guide lifestyle discussions and preventive care.
Fitness and wellness: tracking weight‑for‑height status while remembering BMI’s limits for athletes and muscular body types.
Employers/insurers/wellness programs: standardized categorization for broad population screening with recommended follow‑ups for elevated waist or other risk markers.
Pairing BMI with waist measures and clinical context improves accuracy and actionability across these use cases.
Above‑the‑widget snippet (paste)
Calculate BMI instantly using metric or US units, see adult WHO/CDC categories, and learn when to check waist measures for central fat risk, all in a fast, mobile‑friendly tool.
BMI is a screening index, so review limitations for athletes and children, and use waist thresholds to refine cardiometabolic risk understanding.
Below‑the‑widget copy (paste)
What your BMI means
Underweight: <18.5 may indicate undernutrition or other issues and merits clinical review in context.
Healthy: 18.5–24.9 aligns with lower risk ranges in general surveillance data for adults.
Overweight: 25.0–29.9 suggests elevated risk; consider waist context and lifestyle interventions.
Obesity: ≥30.0 is associated with higher cardiometabolic risk, often subclassified into classes I–III for management.
Children and teens
Use age‑/sex‑specific percentiles rather than adult thresholds to avoid misclassification during growth and development.
Consult pediatric charts and clinicians for individualized interpretation of BMI percentiles and trends.
Waist and risk
Measure waist at the level recommended by health agencies and compare against commonly used thresholds (men >40 in/102 cm, women >35 in/88 cm) for added risk context.
Central adiposity raises risk for diabetes and heart disease, so address waist alongside BMI in prevention planning.
What is BMI and how is it calculated?
BMI is weight divided by height squared—kg/m2 or lbin2×703—used to classify adult weight status in public health.
What are the standard adult categories?
Underweight <18.5, healthy 18.5–24.9, overweight 25.0–29.9, and obesity ≥30.0 (with classes I–III commonly used for ≥30).
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Do Asian populations use different cutoffs?
Many guidelines apply lower thresholds (e.g., overweight ≥23, obesity ≥25) to reflect higher metabolic risk at lower BMI in these populations.
Does BMI diagnose body fatness or health?
No, BMI is a screening index and does not directly measure body fat; consider waist and clinical factors for a fuller assessment.
How should children’s BMI be interpreted?
Use age‑ and sex‑specific percentiles rather than adult categories; for example, obesity is ≥95th percentile for ages 2–20.