BMI Calculator
Calculate your Body Mass Index (BMI) and find out if you are underweight, normal weight, overweight, or obese. Get your healthy weight range and health risk level instantly.
Calculate Your BMI
What is BMI?
Body Mass Index (BMI) is a measurement that uses your height and weight to estimate if you have a healthy body weight. It is widely used by doctors and health organizations as a quick screening tool.
BMI Formula (Metric): BMI = Weight (kg) ÷ Height (m)²
BMI Categories (WHO Standard)
- Underweight: BMI less than 18.5 — may indicate malnutrition or other health issues
- Normal weight: BMI 18.5–24.9 — healthy range, lower risk of chronic diseases
- Overweight: BMI 25–29.9 — increased risk of health conditions
- Obese Class I: BMI 30–34.9 — high risk
- Obese Class II: BMI 35–39.9 — very high risk
- Obese Class III: BMI ≥ 40 — extremely high risk
BMI Limitations
- BMI does not distinguish between muscle and fat mass — athletes may have high BMI despite being healthy
- BMI doesn't account for fat distribution (waist-hip ratio is also important)
- BMI thresholds may differ for Asian populations (overweight threshold is sometimes 23 for Asians)
- Not suitable for children, pregnant women, or elderly as sole health indicator
- Always consult a doctor for proper health assessment
Healthy Tips Based on Your BMI
- Normal BMI: Maintain with regular exercise (150 min/week) and balanced diet
- Overweight: Reduce calorie intake by 500/day, increase physical activity
- Underweight: Increase calorie-dense nutrient-rich foods, strength training
- Obese: Consult a doctor; structured weight loss program recommended
Worked Example
Suppose someone is 1.75 m tall and weighs 80 kg. Their BMI is 80 ÷ (1.75)² = 80 ÷ 3.0625 = 26.1, which falls in the “overweight” range. To reach the top of the normal range (BMI 24.9) at the same height, they would need to weigh about 76 kg — a difference of roughly 4 kg. Seeing the target weight rather than just the category makes the number far more actionable.
Why BMI Should Not Be Used Alone
BMI is a screening tool, not a diagnosis. Because it uses only height and weight, it cannot tell muscle from fat. A muscular athlete and someone carrying excess fat can share the same BMI despite very different health profiles. Two better companions to BMI are waist circumference (a waist over 102 cm for men or 88 cm for women signals higher risk regardless of BMI) and the waist-to-hip ratio, both of which capture where fat is stored — abdominal fat is the most strongly linked to heart disease and diabetes.
BMI for Different Groups
- Asian populations: Health risks rise at lower BMIs, so many guidelines treat 23 as overweight and 27.5 as obese rather than 25 and 30.
- Athletes: High muscle mass can push BMI into the overweight range while body fat remains very low — body-fat measurement is more meaningful here.
- Older adults: A slightly higher BMI can be protective in the elderly; very low BMI may signal frailty or malnutrition.
- Children and pregnant women: Standard adult BMI categories do not apply; specialised growth charts and medical guidance are required.
Better Health Metrics to Track Alongside BMI
For a fuller picture of your health, combine BMI with body-fat percentage, waist circumference, resting heart rate, blood pressure, and blood sugar/cholesterol levels. Sustainable habits — regular activity, balanced nutrition, adequate sleep, and stress management — improve all of these markers together. Always consult a healthcare professional before starting a weight-loss or fitness programme, especially if you have existing health conditions.
Frequently Asked Questions — BMI Calculator
BMI (Body Mass Index) is a simple numerical measure calculated from your height and weight. It is used globally to screen for weight categories — underweight, normal weight, overweight, and obese — that may indicate potential health risks.
For adults, a BMI of 18.5–24.9 is considered normal weight. Below 18.5 is underweight, 25–29.9 is overweight, and 30 or above is classified as obese (with Class I: 30–34.9, Class II: 35–39.9, and Class III: 40+).
BMI is a useful screening tool but not a definitive health measure. It does not distinguish between muscle and fat mass, so muscular athletes may have a high BMI despite low body fat. It also does not account for age, sex, ethnicity, or fat distribution (e.g., abdominal fat).
Research suggests South Asians, including Indians, face higher metabolic risks at lower BMI values. Many Indian health guidelines consider a BMI of 23–27.4 as overweight and 27.5+ as obese — slightly lower thresholds than the standard WHO cutoffs of 25 and 30.
The most effective approach combines a calorie-controlled diet (a 500 kcal/day deficit) with regular physical activity (at least 150 minutes of moderate exercise per week). Even a modest 5–10% reduction in body weight can meaningfully improve metabolic health and reduce disease risk.
Standard BMI thresholds do not apply to children. For those under 18, doctors use BMI-for-age percentile charts that account for normal growth patterns. A child's BMI is interpreted relative to other children of the same age and sex, not against adult cutoffs.