BMI Calculator

Body Mass Index (BMI) is a numerical measure of a person's weight relative to their height. Calculated as weight (kg) divided by height squared (m²), it is used worldwide as a screening tool to classify weight categories — underweight, normal weight, overweight, and obese. While BMI does not directly measure body fat, it is a practical and widely used first-line health assessment.

BMI is calculated using the formula: BMI = weight (kg) ÷ height (m)². For example, a person who is 170 cm (1.70 m) tall and weighs 70 kg has a BMI of 70 ÷ (1.70 × 1.70) = 24.2. In imperial units, the formula is: BMI = [weight (lbs) ÷ height (in)²] × 703.

For Indians and South Asians, the WHO Asian-Pacific guidelines recommend a Normal BMI range of 18.5 to 22.9. Overweight begins at BMI 23 and Obesity at BMI 27.5 — both significantly lower than the Western thresholds of 25 and 30. This is because South Asians carry more visceral (abdominal) fat at lower BMI levels, which raises metabolic and cardiovascular risk earlier.

Research consistently shows that South Asians develop type 2 diabetes, hypertension, and cardiovascular disease at lower BMI values than Western populations. This is due to genetic differences in body fat distribution — South Asians store more fat centrally (around the abdomen and organs) at the same overall BMI. The WHO Expert Consultation in 2004 endorsed lower action thresholds of 23 (overweight) and 27.5 (obese) for Asian populations.

Yes. Using WHO Asian-Pacific guidelines, a BMI of 24.0 falls in the Overweight category for South Asians (range: 23.0–27.4). Under Western standards, BMI 24.0 would be considered Normal. This is an important distinction — at BMI 24, an Indian person has an elevated risk of developing type 2 diabetes and should consider lifestyle modifications.

For a person 170 cm (1.70 m) tall, the healthy weight range using Asian-Pacific guidelines (BMI 18.5–22.9) is approximately 53.5 kg to 66.1 kg (117.9 lbs to 145.8 lbs). Using Western guidelines (BMI 18.5–24.9), the range would be slightly wider at 53.5 kg to 71.9 kg. The Asian-Pacific range is recommended for Indians and South Asians.

For a person 180 cm (1.80 m) tall, the healthy weight range using Asian-Pacific guidelines (BMI 18.5–22.9) is approximately 59.9 kg to 74.1 kg (132.1 lbs to 163.5 lbs). A weight of 90 kg at this height gives a BMI of 27.8, which falls in the Obese category per Asian-Pacific standards and Overweight under Western standards.

BMI has known limitations. It does not differentiate between muscle mass and body fat — athletes may score as overweight despite very low body fat. It also does not account for fat distribution, bone density, age, or gender. For a more complete picture, combine BMI with body fat percentage measurement and waist circumference. For men, a waist over 90 cm (35 in) and for women over 80 cm (31.5 in) indicates elevated risk independent of BMI.

BMI is a simple weight-to-height ratio and does not directly measure body fat. Body fat percentage tells you what proportion of your total body weight is fat tissue. Two people can have the same BMI but very different body compositions — an athlete with high muscle mass and a sedentary person may both have BMI 26, but the athlete has far less body fat. Body fat percentage is a more accurate measure of health and fitness.

The BMI formula and thresholds are the same for men and women. However, women naturally carry more body fat than men at the same BMI due to hormonal and physiological differences. At BMI 22, women typically have about 28–32% body fat, while men have about 18–22%. This means BMI may slightly underestimate health risk in women with low muscle mass and overestimate it in muscular men.

To reach a healthy BMI of 18.5–22.9, create a moderate calorie deficit of 300–500 kcal per day through a combination of diet and exercise. Focus on reducing refined carbohydrates, added sugars, and processed foods while increasing vegetables, lean proteins, and whole grains. Aim for at least 150 minutes of moderate aerobic exercise per week plus 2 strength training sessions. Losing 0.5–1 kg per week is a safe and sustainable rate.

Yes. A person with a normal BMI (18.5–22.9) can still have high visceral fat, poor cardiovascular fitness, or metabolic risk factors — a condition sometimes called "normal weight obesity" or "skinny fat." Conversely, a person with BMI 24 who exercises regularly and has good metabolic markers may be healthier than the number suggests. Always consider waist circumference, body fat percentage, blood pressure, and blood sugar alongside BMI.

A BMI below 18.5 is classified as Underweight for both Asian and Western standards. Being underweight raises the risk of nutrient deficiencies, anaemia, osteoporosis, impaired immune function, and in women, menstrual irregularities. If you are underweight, focus on gradually increasing calorie intake with nutrient-dense foods — whole grains, legumes, dairy, nuts, and lean meats — and consider resistance training to build muscle mass.

Yes. Adult BMI thresholds do not apply to children and teenagers. For individuals aged 2–19, BMI-for-age percentile charts are used instead. A child is classified as underweight if below the 5th percentile, healthy weight between the 5th and 85th percentile, overweight between the 85th and 95th percentile, and obese at or above the 95th percentile. These charts account for normal changes in body composition during growth.

For most adults, checking BMI every 3–6 months is sufficient to track meaningful changes. Since BMI reflects gradual weight changes, daily or weekly checks are unnecessary and can be misleading due to normal weight fluctuations from water retention and digestion. If you are actively trying to gain or lose weight, monthly checks alongside waist measurements give a better picture of progress.