BMI calculator
Not medical advice: this tool is only a general estimate. It does not diagnose, treat, or replace professional medical advice. Inputs stay in your browser.
How to use this tool
Enter weight in kilograms and height in centimeters to estimate adult BMI and its range. The result is for general screening and personal tracking, not diagnosis.
Enter height and weight to calculate BMI as kilograms divided by squared height in metres. Use this adult estimate for weight tracking, not a medical diagnosis.
💡 3 Quick Steps to Get Started
Enter height in centimetres, for example 200 cm.
Enter weight in kilograms, for example 96 kg.
The example gives BMI 24. All four locales use the same cutoffs: below 18.5 underweight; 18.5 to below 25 normal; 25 to below 30 overweight; 30 or above obese.
When it helps
Use it for a quick height-and-weight BMI check, while recognizing that it cannot reflect muscle mass, pregnancy, illness, or individual health risk.
How it works
BMI equals weight in kilograms divided by height in meters squared. The result is rounded to two decimals and grouped using common adult boundaries of 18.5, 25, and 30.
Worked example
At 175 cm and 70 kg, BMI is 22.86, which falls in the common adult normal range from 18.5 to under 25.
Limits and data handling
Missing, non-finite, non-positive, or out-of-range values produce no result. BMI uses only height and weight, so it cannot reflect muscle mass, pregnancy, illness, or personal risk and cannot diagnose or treat.
Height and weight are calculated only in your current browser. Analytics may record the tool identifier, category, and locale, but not your health inputs or calculated result.
Body Mass Index (BMI) & Body Composition Guide
1. What Is Body Mass Index (BMI)? Origins and Method
The tool uses shared adult cutoffs 18.5 / 25 / 30 in all four languages, without regional switching. Regional standards below are context, not this tool’s classification or a diagnosis.
Body Mass Index (BMI) is a standardized metric developed by Belgian polymath Adolphe Quetelet in the 19th century. It quantifies the relationship between an individual’s body weight and stature, establishing a universally recognized baseline for broad population health assessments.
The calculation divides weight in kilograms by the square of height in meters. In the imperial system, weight in pounds is multiplied by 703 and divided by height in inches squared. BMI provides a quick, zero-cost screening tool used by healthcare systems worldwide.
2. World Health Organization (WHO) Adult BMI Classifications
The World Health Organization categorizes adult nutritional status according to the following thresholds: Underweight (< 18.5), Normal weight (18.5 to 24.9), Overweight (25.0 to 29.9), and Obesity (Class I: 30.0-34.9, Class II: 35.0-39.9, Class III: ≥ 40.0).
Staying within the healthy range correlates with a reduced statistical incidence of hypertension, type 2 diabetes, coronary artery disease, and stroke.
- Underweight (< 18.5): Potential risks of nutritional deficiency and decreased bone density.
- Normal weight (18.5–24.9): Optimal baseline for cardiovascular and metabolic markers.
- Overweight & Obese (≥ 25.0): Increased likelihood of metabolic syndrome and joint stress.
3. Limitations of BMI: Muscle Mass vs. Adiposity
While effective as an epidemiological baseline, BMI has distinct diagnostic limitations for individuals because it cannot differentiate between fat mass, bone density, and muscle tissue.
Athletes and strength-trained individuals often register in the "overweight" or "obese" categories due to dense muscular hypertrophy despite low body fat percentages. Conversely, older adults or sedentary individuals may exhibit "normal" BMI while carrying excess visceral fat (sarcopenic obesity). Health practitioners recommend pairing BMI with waist-to-hip ratios and bioelectrical impedance body composition scans.
4. Evidence-Based Principles for Metabolic Wellness
Sustainable weight management prioritizes metabolic biomarkers over rapid scale weight drops. Emphasize a nutrient-dense whole-food diet, adequate dietary protein, regular resistance training to preserve lean tissue, and at least 150 minutes of moderate cardiovascular activity weekly.
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FAQ
BMI calculator: What information do I enter?
Enter a weight greater than 0 and no more than 500 kg, plus a height greater than 0 and no more than 300 cm. No name, age, or medical history is required.
BMI calculator: How are BMI and its range calculated?
Weight in kilograms is divided by height in meters squared and rounded to two decimals. The adult ranges are below 18.5, 18.5 to under 25, 25 to under 30, and 30 or above.
BMI calculator: Which limits or errors should I consider?
Missing, non-finite, non-positive, or out-of-range values produce no result. BMI uses only height and weight, so it cannot reflect muscle mass, pregnancy, illness, or personal risk and cannot diagnose or treat.
BMI calculator: How are my health values handled?
Height and weight are calculated only in your current browser. Analytics may record the tool identifier, category, and locale, but not your health inputs or calculated result.