Calculate your BMI using metric or imperial units. Understand your weight category and get health insights.
Body Mass Index (BMI) is a measure of body fat based on your weight in relation to your height. It applies to adult men and women and is a useful screening tool for weight categories that may lead to health problems.
Enter your height and weight to calculate BMI
Body Mass Index (BMI) represents a standardized measurement derived from an individual's mass (weight) and height. Calculated as body mass divided by the square of body height, BMI is expressed in units of kg/m². This measurement originated in the 19th century through the work of Belgian statistician Adolphe Quetelet and has evolved into a globally recognized screening tool for weight categorization.
The fundamental BMI formula operates on a straightforward principle: BMI = weight (kg) ÷ height² (m). For imperial measurements, the calculation transforms to BMI = (weight (lbs) ÷ height² (in)) × 703.
BMI = weight (kg) / (height (m))²
BMI = (weight (lb) × 703) / (height (in))²
For example, a person who weighs 70 kg and is 1.75 m tall would calculate their BMI as follows:
BMI = 70 / (1.75 × 1.75) = 22.86
Modern medical practice employs BMI as an initial screening instrument rather than a diagnostic tool. The World Health Organization (WHO) established international BMI classifications that define underweight (below 18.5), normal weight (18.5–24.9), overweight (25–29.9), and obese (30+) categories.
BMI classifications provide a standardized framework for understanding weight-related health risks. Each category correlates with specific health considerations and recommended actions.
| BMI Range | Classification | Health Considerations | Recommended Actions |
|---|---|---|---|
| < 18.5 | Underweight | Potential nutritional deficiencies, osteoporosis risk, weakened immunity | Nutritional assessment, gradual weight gain strategy, medical consultation |
| 18.5 – 24.9 | Normal Weight | Optimal health range, lowest mortality risk from weight-related conditions | Maintenance through balanced diet and regular physical activity |
| 25.0 – 29.9 | Overweight | Increased cardiovascular risk, potential metabolic changes | Moderate weight loss (5–10% of body weight), lifestyle modifications |
| 30.0 – 34.9 | Obese Class I | Significant health risk elevation, likely metabolic syndrome indicators | Structured weight management program, medical supervision |
| 35.0 – 39.9 | Obese Class II | High risk of comorbidities, substantial quality of life impact | Comprehensive medical intervention, potential pharmacological treatment |
| ≥ 40.0 | Obese Class III | Severe health risks, significant mortality increase | Multidisciplinary medical care, potential surgical consideration |
Comprehensive BMI classification chart based on WHO standards
Our intuitive BMI calculator delivers instant results through a streamlined three-step process designed for maximum accuracy and user convenience.
Begin by entering your age and selecting your gender. For children and adolescents (ages 2–19), these details enable percentile calculations based on CDC growth charts. Adult calculations (20+ years) utilize standard BMI categories regardless of gender, though age provides context for result interpretation.
Select your preferred measurement system—metric (centimeters and kilograms) or imperial (feet/inches and pounds). Input your current height and weight values. The calculator automatically converts between systems and displays your healthy weight range based on height alone.
Upon calculation, you'll receive your BMI numerical value, weight category, personalized health insights, and visual representations on our interactive BMI meter and chart. The system also generates tailored recommendations based on your specific results.
For optimal accuracy, measure height without shoes and weight with minimal clothing. Morning measurements typically provide the most consistent results as body weight fluctuates throughout the day.
BMI interpretation differs fundamentally between adults and children due to dynamic growth patterns and developmental variations.
For individuals aged 20 years and above, BMI interpretation follows standardized international classifications established by the World Health Organization. These categories apply uniformly across adult populations regardless of gender, though research indicates subtle variations in optimal ranges between sexes.
Children and adolescent BMI interpretation diverges from adult classifications. The Centers for Disease Control and Prevention (CDC) utilize age- and sex-specific percentiles rather than fixed numeric thresholds.
CDC BMI-for-age growth chart illustrating percentile-based classifications
Extensive epidemiological research establishes clear correlations between BMI classifications and specific health outcomes.
| Health Condition | Overweight Risk Increase | Obese Risk Increase | Mechanisms |
|---|---|---|---|
| Type 2 Diabetes | 3x | 7x | Insulin resistance, pancreatic stress |
| Hypertension | 2x | 4x | Volume overload, sympathetic activation |
| Coronary Artery Disease | 1.5x | 2.5x | Dyslipidemia, endothelial dysfunction |
| Sleep Apnea | 2x | 4x | Airway compression, ventilatory control |
| Osteoarthritis | 1.5x | 3x | Mechanical loading, inflammation |
| Certain Cancers | 1.3x | 1.5–2x | Hormonal, inflammatory pathways |
Type 2 diabetes risk shows the strongest BMI correlation—each 5-unit increase raises risk approximately 67%. Cardiovascular conditions follow closely, with 29% higher coronary disease risk per 5 BMI units.
Sustainable BMI management integrates nutritional science, behavioral psychology, and physiological principles.
Prioritize nutrient density over calorie counting alone. The Mediterranean dietary pattern—emphasizing vegetables, fruits, whole grains, legumes, nuts, and olive oil—demonstrates superior weight maintenance outcomes.
The American College of Sports Medicine recommends 150–250 minutes weekly of moderate activity for weight maintenance, with 250+ minutes for weight loss. Optimal programming includes resistance training twice weekly and daily movement.
Successful weight maintainers demonstrate common behaviors: consistent breakfast consumption, weekly self-weighing, 60+ minutes daily activity, and limited television viewing.
While valuable for population screening, BMI possesses well-documented limitations in individual assessment.
Body Composition Blindness: BMI cannot distinguish between lean mass and adipose tissue. Athletic individuals with elevated muscle mass frequently register falsely elevated BMI values.
Fat Distribution Ignorance: Central adiposity (abdominal fat) demonstrates stronger metabolic and cardiovascular correlations than peripheral fat. Waist circumference provides superior risk stratification.
Ethnic Variations: Asian populations experience elevated metabolic risks at lower BMIs, prompting revised thresholds: overweight (23–27.4) and obese (≥27.5).
Prioritize whole foods over processed alternatives—each 10% increase in ultra-processed food consumption correlates with 12% higher obesity risk. Emphasize protein (0.8–1.2g/kg) and fiber (30g+ daily) for satiety and metabolic benefits.
Incorporate resistance training twice weekly alongside 150+ minutes of moderate cardio. Non-exercise activity thermogenesis (NEAT) accounts for substantial calorie expenditure—increase standing, walking, and daily movement.
Achieve 7–9 hours quality sleep nightly—sleep deprivation disrupts leptin/ghrelin balance, increasing appetite 20–25%. Maintain consistent sleep schedules and create dark, cool sleeping environments.
Chronic elevation elevates cortisol, promoting abdominal fat deposition. Implement daily stress-reduction practices: mindfulness meditation, nature exposure, deep breathing, or progressive muscle relaxation.
Consume 30–35ml water per kg body weight daily. Pre-meal water consumption reduces calorie intake 13%. Replace sugar-sweetened beverages with water—each daily serving increase correlates with 0.5kg annual weight gain.
Consider time-restricted eating within 8–12 hour windows—research demonstrates metabolic benefits independent of calorie reduction. Avoid late-night eating, particularly within 3 hours of bedtime.
Calculator Premium offers specialized tools for comprehensive health management. Each calculator provides accurate, instant results with detailed explanations.
This BMI calculator provides estimates based on standard formulas and should not replace professional medical advice. Individual health status depends on numerous factors beyond BMI measurements.
Consult healthcare professionals for personalized health assessments, particularly if your BMI indicates underweight, overweight, or obese categories. This tool serves educational purposes and cannot diagnose medical conditions.
Calculator Premium ensures calculation accuracy but recommends verification with healthcare providers for medical decisions. Results represent statistical probabilities rather than individual certainties.