BMI Calculator
Calculate your Body Mass Index in metric or imperial units, see where it falls on the scale, and find your healthy weight range.
What BMI does (and doesn't) tell you
Body Mass Index is a quick screening number — weight relative to height — used by doctors as a starting point, not a diagnosis. It doesn't distinguish muscle from fat, so very muscular people can show as "overweight" despite low body fat, and it doesn't account for bone structure, age, or where fat is carried. Use it as one data point, and talk to a healthcare provider for a full picture.
Frequently asked questions
How is BMI calculated?
Metric: weight in kilograms divided by height in meters squared. Imperial: 703 × weight in pounds divided by height in inches squared. Both formulas give the same result for the same body — this calculator supports either unit system.
What do the BMI categories mean?
For adults: under 18.5 is underweight, 18.5–24.9 is normal weight, 25–29.9 is overweight, and 30+ is obese. These are the standard WHO/CDC adult ranges used by most healthcare providers as a screening starting point.
Is BMI accurate for everyone?
No — it doesn't distinguish muscle from fat, so athletes and very muscular people often show a higher BMI despite low body fat. It also doesn't apply the same way to children/teens (see the age note) or account for bone density, age, or fat distribution. Treat it as a screening tool, not a diagnosis.
Is my height and weight data stored?
No. Everything is calculated instantly in your browser with JavaScript — nothing is uploaded, logged, or stored.