BMI Calculator

BMI is your weight in kilograms divided by your height in metres squared. Between 18.5 and 25 counts as normal weight under the WHO scale. It does not distinguish muscle from fat.

Body mass index is a screening tool, not a diagnosis. It divides your weight by the square of your height, which is why the unit is kg/m², and places the result on the scale the WHO and CDC share: below 18.5 is underweight, 18.5 to 24.9 healthy weight, 25.0 to 29.9 overweight, and 30.0 and above obesity, which the same table splits further at 35.0 and 40.0. The imperial version — pounds divided by inches squared, times 703 — lands on the same number. Read the result as a flag rather than a verdict. A value outside the healthy band is a reason to look further, at blood pressure, waist circumference, family history and activity, not a conclusion on its own. The caveat that matters most is that BMI measures excess weight, not excess fat. It cannot tell muscle from bone from fat, so a trained athlete can land in the overweight band with very little body fat: in one study, men who all shared a BMI of 27 kg/m² had body fat percentages ranging from 10 to 32 percent. It also ignores where fat sits — visceral fat around the abdominal organs carries far more metabolic risk than fat on hips and thighs — so someone with a healthy BMI can still be carrying exactly the risk the number was meant to catch.