BMI Calculator

BMI (Body Mass Index) is a number derived from height and weight: BMI = weight (kg) divided by height squared (m²). For example, a person who is 170 cm tall and weighs 70 kg has a BMI of 70 divided by 1.70² = 24.2, which falls in the normal range. In imperial units, BMI = (weight in lbs × 703) divided by height in inches squared.

The World Health Organization defines four main categories: Underweight (below 18.5), Normal weight (18.5–24.9), Overweight (25–29.9), and Obese (30 and above). Obesity is further split into Class 1 (30–34.9), Class 2 (35–39.9), and Class 3, also called severe obesity (40 and above). A healthy BMI range for most adults is 18.5 to 24.9.

For most adults, a healthy BMI is between 18.5 and 24.9. Values below 18.5 signal underweight; 25 to 29.9 is overweight; 30 or above is obese. These are population-level thresholds from the WHO and apply to adults aged 20 and older. Children and teenagers are assessed differently using age- and sex-specific growth charts.

The WHO BMI formula and category thresholds are identical for men and women. However, at the same BMI, women typically carry more body fat than men, and men carry more muscle mass. This means the same BMI number can indicate different health profiles by sex. BMI is a screening tool, not a precise body composition measurement.

Yes. BMI cannot distinguish muscle from fat. A rugby player or bodybuilder with high muscle mass may have a BMI in the overweight or obese range while having very low body fat. For athletes, body fat percentage measured by DEXA scan or skinfold calipers is a more meaningful metric than BMI alone.

BMI is a population-level screening tool, not a personal health diagnosis. It does not account for muscle mass, age, sex, or where body fat is distributed. Waist circumference (above 94 cm for men, 80 cm for women signals elevated risk) and body fat percentage give a more complete picture alongside BMI.

Research shows South Asians, including Indians, develop metabolic complications at lower BMI thresholds than Western populations. Many Indian guidelines set the overweight threshold at 23 and obese at 25, versus the WHO's 25 and 30. This tool uses standard WHO thresholds for global comparability; consult a doctor for personalised advice.

Switch the toggle to Imperial (Ft, Lbs) mode. Enter feet and inches in the two separate height fields and your weight in pounds. The tool converts internally and displays your BMI instantly. You don't need to convert to centimetres manually.

For most adults, checking BMI once every few months alongside other health markers is sufficient. BMI is most useful for tracking trends over time rather than as a single reading. If you are making changes to diet or activity, monthly checks can help confirm progress.