BMI Calculator
Calculate your Body Mass Index — includes WHO and Asian BMI categories.
What Is BMI?
BMI (Body Mass Index) is a numerical value calculated from a person's height and weight. It is used worldwide as a screening tool to identify weight categories — underweight, normal, overweight, and obese — that may indicate potential health risks. BMI is calculated using the formula: BMI = weight (kg) ÷ height (m)². For example, a person who is 1.75m tall and weighs 70kg has a BMI of 70 ÷ (1.75 × 1.75) = 22.9, which falls in the normal range.
BMI Chart — Categories and Ranges
WHO Standard BMI Categories (global):
Underweight: below 18.5 | Normal weight: 18.5 – 24.9 | Overweight: 25.0 – 29.9 | Obese Class I: 30.0 – 34.9 | Obese Class II: 35.0 – 39.9 | Obese Class III (morbid obesity): 40.0 and above
WHO Asian BMI Categories (for Asian populations):
Underweight: below 18.5 | Normal: 18.5 – 22.9 | Overweight: 23.0 – 24.9 | Obese Class I: 25.0 – 29.9 | Obese Class II: 30.0 and above
Asian populations have been shown to face increased health risks (type 2 diabetes, cardiovascular disease) at lower BMI values than Western populations, which is why the WHO adopted different cut-off points for Asian adults.
How Is BMI Calculated?
Metric formula: BMI = weight (kg) ÷ [height (m)]². Example: 70 kg ÷ (1.75 m × 1.75 m) = 22.86
Imperial formula: BMI = [weight (lbs) ÷ height (inches)²] × 703. Example: 154 lbs ÷ (69 inches × 69 inches) × 703 = 22.75
Both formulas give the same result. The calculator above handles both metric and imperial units automatically.
Healthy Weight Range
To find your healthy weight range for your height, rearrange the formula: Healthy weight (kg) = BMI × [height (m)]². For a normal BMI of 18.5–24.9, a person who is 1.70m tall has a healthy weight range of 18.5 × 1.70² to 24.9 × 1.70² = 53.5 kg to 71.9 kg. The calculator above shows your specific healthy weight range after calculating your BMI.
BMI Limitations — What BMI Doesn't Tell You
BMI is a useful first-step screening tool, but it has well-known limitations. It does not distinguish between muscle mass and fat mass — athletes with high muscle mass may be classified as overweight despite having low body fat. It doesn't account for fat distribution — abdominal (visceral) fat is more dangerous than fat elsewhere, but BMI doesn't capture this. It also doesn't adjust for age, sex, or ethnicity beyond the WHO Asian cut-offs. BMI is a screening indicator, not a diagnostic tool. Always consult a healthcare professional for a complete health assessment.
BMI for Men vs Women
The standard BMI formula and categories are the same for men and women. However, women naturally have a higher proportion of body fat at the same BMI than men — a BMI of 22 in a woman corresponds to approximately 30% body fat, while in a man it corresponds to approximately 22% body fat. Some health experts argue for sex-specific BMI cut-offs, but WHO still uses the same ranges for both sexes. The calculator applies the same WHO standard regardless of sex.