Calculateur d'IMC — Indice de Masse Corporelle

L'IMC (Indice de Masse Corporelle) est une mesure qui rapporte votre poids à votre taille pour évaluer votre état pondéral chez les adultes. Un IMC compris entre 18,5 et 24,9 est considéré comme normal pour la majorité des personnes.

Ce calculateur accepte les unités métriques (kilogrammes et centimètres) ainsi que les unités américaines (livres et pouces). Entrez votre âge, sexe, taille et poids pour obtenir votre résultat instantanément avec une interprétation de votre catégorie de poids.

BMI Calculator

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Calculate your Body Mass Index (BMI) using US or metric units. Understand your results with categories based on WHO guidelines and get AI-powered health insights.

⚖️ Details

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Age

years

Gender

Height

Weight

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💡BMI is a screening tool, not a diagnostic measure. Results should be interpreted alongside other health indicators.

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📚 In-Depth Guide

This calculator is part of a comprehensive guide

The Complete BMI Guide 2026: Formula, Charts, Healthy Ranges & Alternatives

Full Guide

The definitive 2026 BMI guide: metric and imperial formulas with worked examples, WHO/CDC adult categories, Asian-adjusted thresholds, children's BMI percentile charts, athlete limitations, disease risk associations, waist-to-height ratio, body fat percentage alternatives, and 10 evidence-based strategies to reach a healthy weight. Includes free BMI, calorie, and body fat calculators.

View all guides →

Body Mass Index (BMI) is a number calculated from weight and height using the formula BMI = weight (kg) ÷ height² (m²). The World Health Organization (WHO) defines four categories: Underweight (< 18.5), Normal weight (18.5–24.9), Overweight (25–29.9), and Obese (≥ 30). For adults aged 20+, the same thresholds apply regardless of age or sex. A healthy BMI reduces risk of cardiovascular disease, type 2 diabetes, and hypertension — though clinicians interpret BMI alongside waist circumference and body fat percentage for a complete picture.

📊 Body Mass Index — Complete Guide

Reviewed by CalculatorApp.me Health Editorial Team · Updated March 2026 · 10 min read

🔬 Evidence-Based

650M+

Adults obese worldwide

1832

Year BMI was invented

18.5–25

Healthy BMI range

WHO

International standard

Jump to:

What is BMI?Formula Categories History Examples Limitations vs Body Fat Ethnicity FAQ

📊 What Is BMI?

Body Mass Index (BMI) is a numerical value calculated from a person's weight and height. Clinicians use it as a screening tool to categorize underweight, normal weight, overweight, and obesity in adults. BMI does not directly measure body fat but correlates with direct measures and offers an inexpensive, scale-and-tape alternative.

The World Health Organization (WHO) recognizes BMI as the standard measure for population-level obesity surveillance. Clinicians worldwide use it as an initial screening tool, though they interpret it alongside other health indicators.

Adults with a BMI of 18.5–24.9 carry the lowest health risk. Values outside this range raise the risk of cardiovascular disease, type 2 diabetes, hypertension, and certain cancers.

Key BMI Facts

📏Derived from weight (kg) ÷ height² (m²)

🌍WHO, CDC, and NIH rely on it as their primary screening tool

⚖️Tracks body fat percentage trends across most adult populations

🏥Clinicians use it worldwide to assess health risk

🔢Simple calculation requiring only two measurements

Ideal Weight Calculator →Body Fat Calculator →BMR Calculator →

🧮 The BMI Formula

Metric Formula

BMI = weight (kg) ÷ height² (m²)

Example: 70 kg person, 1.75 m tall

BMI = 70 ÷ (1.75)² = 70 ÷ 3.0625 = 22.9

Imperial Formula

BMI = (weight (lbs) × 703) ÷ height² (in²)

Example: 154 lbs person, 5'9" (69 in)

BMI = (154 × 703) ÷ (69)² = 108,262 ÷ 4761 = 22.7

📋 WHO BMI Classification

BMI Range	Classification	Health Risk	Action
< 18.5	Underweight	Moderate risk	Get a nutritional assessment
18.5 – 24.9	Normal weight	Lowest risk	Maintain healthy habits
25.0 – 29.9	Overweight	Increased risk	Make lifestyle changes
30.0 – 34.9	Obese Class I	High risk	Consult a physician
35.0 – 39.9	Obese Class II	Very high risk	Start medical treatment
≥ 40.0	Obese Class III	Extremely high risk	Seek urgent medical care

Source: World Health Organization (WHO) Global Database on Body Mass Index

📜 History of BMI

1832Quetelet Index Created

Belgian mathematician Adolphe Quetelet develops the weight-to-height ratio as part of his study of human physical characteristics and social statistics. Called the "Quetelet Index," Quetelet never designed it as a health measure.

1972Ancel Keys Renames It "BMI"

American physiologist Ancel Keys publishes a landmark paper in the Journal of Chronic Diseases analyzing seven countries. He renames Quetelet's index "Body Mass Index" and promotes it as the best available proxy for body fat in population studies.

1985NIH Adopts BMI

The U.S. National Institutes of Health adopts BMI as a standard measure for adiposity research and clinical assessment.

1995WHO Global Standards

The World Health Organization establishes international obesity classification standards using BMI cutoffs: 25 for overweight and 30 for obesity.

2013AMA Recognition

The American Medical Association formally designates obesity (BMI ≥ 30) as a disease, elevating the importance of BMI screening in clinical practice.

2023Limitations Acknowledged

Major medical organizations including the AMA begin recommending BMI as one tool among many, acknowledging its limitations regarding body composition, ethnicity, and muscle mass.

📝 Worked Examples

Normal Weight

Weight:68 kg

Height:1.72 m

Calculation:68 ÷ 2.96

BMI:23.0

✓ Normal Weight

Overweight

Weight:90 kg

Height:1.75 m

Calculation:90 ÷ 3.06

BMI:29.4

⚠ Overweight

Obese Class I

Weight:100 kg

Height:1.70 m

Calculation:100 ÷ 2.89

BMI:34.6

⚠ Obese Class I

⚠️ Limitations of BMI

❌ Cannot distinguish fat from muscle

Athletes with high muscle mass may score a high BMI yet carry minimal body fat, producing a false obesity reading.

❌ Does not measure body fat distribution

Abdominal obesity (apple shape) carries higher risk than peripheral fat. BMI gives no information about where fat is stored.

❌ Age-related inaccuracy

Older adults tend to lose muscle mass and gain fat with age. The same BMI may represent more body fat in elderly populations.

❌ Ignores bone density

People with higher bone density may have higher BMI without excess fat, and those with osteoporosis may have lower BMI.

❌ Pregnancy limitations

BMI does not reliably indicate health status during pregnancy, as body composition and fluid distribution change substantially.

❌ Does not reflect metabolic health

“Metabolically healthy obese” individuals exist, while normal-weight individuals can have metabolic disorders.

⚖️ BMI vs. Body Fat vs. Ideal Weight

Metric	BMI	Body Fat %	Ideal Weight
Measures	Weight/height ratio	Actual fat tissue %	Target weight range
Accuracy	Low for individuals	High (DEXA, Navy)	Moderate
Equipment	Scale + tape measure	Calipers or DEXA	Scale + tape measure
Cost	Free	$0–$500	Free
Best for	Population screening	Body composition	Weight goal setting
Limitations	Ignores composition	Method variability	Formula variability

Try Body Fat Calculator →Try Ideal Weight Calculator →

🌏 Ethnicity & BMI Adjustments

Research shows that at the same BMI, people of Asian descent have higher body fat percentages and greater cardiometabolic risk compared to White populations. The WHO Expert Consultation recommends lower BMI cutoffs for Asian populations.

Standard WHO Cutoffs (General)

Underweight< 18.5

Normal18.5–24.9

Overweight25.0–29.9

Obese≥ 30.0

Asian-Pacific Cutoffs (WHO Revised)

Underweight< 18.5

Normal18.5–22.9

Overweight (at risk)23.0–27.5

Obese≥ 27.5

Source: WHO Expert Consultation (2004). “Appropriate body-mass index for Asian populations.” The Lancet, 363(9403), 157–163.

🩺 Expert Guidance by BMI Range

Underweight (BMI < 18.5)

Consult a physician to rule out malnutrition, eating disorders, or underlying illness. A registered dietitian can help create a calorie and nutrient-rich eating plan. Strength training builds lean mass safely.

Normal Weight (18.5–24.9)

Focus on maintaining with a balanced diet rich in vegetables, lean proteins, and whole grains. Engage in at least 150 minutes of moderate aerobic activity weekly per CDC/AHA guidelines.

Overweight (25–29.9)

A 5–10% weight reduction significantly reduces cardiovascular and metabolic risk. Start with a modest calorie deficit of 250–500 kcal/day. Use our Calorie Deficit Calculator to plan your approach.

Obese (BMI ≥ 30)

Schedule a medical evaluation. Structured programs combining diet, exercise, and behavioral therapy achieve the best outcomes. Doctors may recommend pharmacotherapy or bariatric surgery for BMI ≥ 35 with comorbidities.

🔬 Key Research on BMI

WHO Fact Sheet

Obesity and Overweight

Current WHO statistics on global obesity prevalence and BMI classification guidance.

who.int ↗

CDC Guidelines

About Adult BMI

CDC guidance on interpreting BMI for adults with health risk information and next steps.

cdc.gov ↗

NEJM Study

BMI and Mortality Risk

Berrington de Gonzalez et al. (2010). BMI and mortality in 1.46 million white adults.

nejm.org ↗

🔍 BMI Myths vs. Facts

✕ Myth

BMI directly measures body fat

✓ Fact

BMI is a proxy calculation based only on weight and height. It estimates fatness but does not directly measure adipose tissue.

✕ Myth

A normal BMI means you're healthy

✓ Fact

Someone can have normal BMI but high body fat (“skinny fat” / normal-weight obesity) with significant metabolic risk.

✕ Myth

BMI thresholds are the same globally

✓ Fact

Asian populations face higher health risks at lower BMI values. WHO recommends lower cutoffs (23 for overweight) for Asian populations.

✕ Myth

Muscle mass doesn't affect BMI

✓ Fact

Muscle is denser than fat. Athletes and bodybuilders frequently score “overweight” or “obese” BMI despite minimal body fat percentages.

❓ Frequently Asked Questions

What is a healthy BMI for adults?+

The WHO defines a healthy adult BMI as 18.5–24.9. Optimal ranges may differ based on age, sex, ethnicity, and body composition.

Is BMI accurate for athletes?+

No. Athletes with high muscle mass frequently register as "overweight" or "obese" despite carrying minimal body fat. BMI overestimates adiposity in muscular individuals. Measure body fat percentage directly for a more accurate assessment.

How does BMI differ for men vs. women?+

The same BMI thresholds apply to both sexes, but women typically have 5–10% more body fat than men at the same BMI due to physiological differences in sex hormones and body composition.

At what BMI is weight loss recommended?+

Medical guidelines recommend weight loss for BMI ≥ 25 with obesity-related comorbidities, or BMI ≥ 30 regardless of other conditions. Always consult a physician.

Can BMI be used for children?+

Children use BMI-for-age percentiles rather than absolute values. A pediatric BMI calculator accounts for age and gender. This adult calculator does not apply to those under 18.

How often should I calculate my BMI?+

Healthy adults should check BMI every 1–2 years. During active weight management, track it monthly so you can monitor your progress directly.

What BMI is considered morbidly obese?+

BMI ≥ 40 defines morbid obesity (also called Class III obesity). At this level, surgical interventions such as bariatric surgery may be considered.

Does BMI change with age?+

Your BMI changes as your weight and height change. Older adults often experience muscle loss (sarcopenia) which can keep BMI stable even as body fat percentage rises.

How accurate is BMI for South Asian populations?+

South Asians tend to develop metabolic disease at lower BMIs. The WHO and many Asian health bodies recommend an overweight threshold of 23 (instead of 25) for South and East Asian populations.

Can a low BMI be dangerous?+

Yes. BMI < 18.5 raises the risk of nutritional deficiencies, bone density loss, immune dysfunction, and in severe cases, cardiac complications and organ failure.

What is BMI Prime?+

BMI Prime is the ratio of your BMI to the upper limit of normal BMI (24.9). A value of 1.0 or less means you're within the normal range. It allows quick comparison regardless of the absolute BMI value.

Should I use BMI to track weight loss progress?+

BMI can serve as one indicator, but waist circumference, body fat percentage, and muscle mass provide a more complete picture. Combining BMI with our Calorie Deficit and Body Fat calculators gives better insight.

References & Further Reading

1.WHO Expert Consultation (2004). Appropriate body-mass index for Asian populations. The Lancet, 363(9403), 157–163. View ↗
2.Keys A, et al. (1972). Indices of relative weight and obesity. Journal of Chronic Diseases, 25(6), 329–343. View ↗
3.Berrington de Gonzalez A, et al. (2010). Body-Mass Index and Mortality. NEJM, 363, 2211–2219. View ↗
4.World Health Organization. (2021). Obesity and overweight. WHO Fact Sheet. View ↗
5.National Institutes of Health. (1998). Clinical guidelines on identification, evaluation, and treatment of overweight and obesity in adults. View ↗
6.Centers for Disease Control and Prevention. (2022). About Adult BMI. View ↗