BMI Calculator
BMI Calculator — Body Mass Index
Supports metric (kg/cm) and imperial (lb/ft·in) — includes ideal weight range and health category
Enter your details on the left and click Calculate BMI to see your results here.
| BMI Range | Category | Health Risk |
|---|---|---|
| < 18.5 | Underweight | Malnutrition risk |
| 18.5 – 24.9 | Normal Weight | Low risk |
| 25.0 – 29.9 | Overweight | Moderate risk |
| 30.0 – 34.9 | Obese Class I | High risk |
| 35.0 – 39.9 | Obese Class II | Very high risk |
| ≥ 40.0 | Obese Class III | Extremely high risk |
Instant Results
Click Calculate to see your category, ideal weight, and body fat estimate right away.
Metric & Imperial
Switch seamlessly between kg/cm and lbs/ft·in — all values convert automatically.
Visual BMI Gauge
A color-coded scale shows exactly where your BMI sits across all WHO weight categories.
Understanding BMI
What is BMI and How is it Calculated?
A complete guide to Body Mass Index — what it measures, its limits, and how to use it wisely
Body Mass Index (BMI) is a numerical value derived from a person's weight and height. Developed by Belgian mathematician Adolphe Quetelet in the 1830s (originally called the Quetelet Index), it was adopted by the World Health Organization (WHO) as a standard screening tool to classify weight status and identify potential health risks linked to excess body fat.
BMI is widely used by doctors, dietitians, and public health bodies because it is simple, non-invasive, and free — requiring only a weighing scale and a measuring tape. In India, BMI is the primary tool used in clinical settings and government health surveys to assess the nutritional status of adults across different regions.
BMI is calculated using a straightforward formula that divides weight by the square of height:
For adults aged 20 and above, the result is interpreted using the same fixed BMI thresholds regardless of age or gender — a BMI below 18.5 is underweight, 18.5–24.9 is normal, 25–29.9 is overweight, and 30 or above falls into one of three obese categories. For children and teenagers (ages 2–19), BMI is plotted on age- and sex-specific growth charts as a percentile, not a fixed number.
Associated with nutrient deficiencies, weakened immunity, anemia, and bone density loss. May signal an underlying health condition requiring medical evaluation.
Associated with the lowest risk of weight-related diseases. Maintaining a BMI in this range through balanced diet and regular activity is the general health target for adults.
Moderate increased risk of type 2 diabetes, hypertension, and cardiovascular disease. Lifestyle changes — diet and exercise — can bring BMI back to the normal range.
High risk of metabolic syndrome, sleep apnea, fatty liver disease, and joint problems. Medical guidance and structured weight management programs are recommended.
Very high risk. At this stage, weight-related complications are likely already present. Bariatric evaluation and intensive intervention may be considered.
Extremely high health risk. Also called severe or morbid obesity — strongly associated with reduced life expectancy. Surgical intervention (bariatric surgery) is often discussed at this level.
BMI cannot distinguish between muscle mass and fat mass. A highly muscular athlete may have a high BMI yet be perfectly healthy, while someone with a normal BMI may carry excess visceral fat.
Research shows Asian populations, including South Asians, carry metabolic risk at lower BMI values. The WHO now uses lower cut-offs of 23 (overweight) and 27.5 (obese) for Asian adults.
As people age, muscle mass decreases and fat redistributes — especially to the abdomen. Older adults may have a "normal" BMI but carry dangerous levels of visceral fat around internal organs.
BMI does not account for where fat is stored. Abdominal (central) fat is far more harmful than fat stored in hips or thighs. Waist circumference is a better indicator of visceral fat risk.