BMI Calculator

Body Mass Index is a single number derived from your weight and height that estimates whether your weight sits in a healthy range for your stature. It is used as a quick population screening measure, not as a direct reading of body fat.

In metric, BMI is weight in kilograms divided by height in metres squared, so 70 kg and 1.75 m gives 70 / 3.0625 = 22.9. In imperial, the formula is 703 times pounds divided by height in inches squared, so 154 lb and 69 in gives 22.7. Both routes reach the same number for the same body.

The World Health Organization bands are: below 18.5 is underweight, 18.5 up to 25 is normal weight, 25 up to 30 is overweight, and 30 or above is obesity. This tool labels your result with the band it falls in.

For most adults a BMI from 18.5 to just under 25 is considered the healthy range. The ideal target can shift with age, sex, muscle mass and ethnicity, so treat the band as a guide rather than a hard line.

The result is rounded to one decimal, which is the level of precision that is meaningful for a screening figure. Rounding happens before the category is chosen, so a value like 24.96 is shown as 25.0 and lands in the overweight band.

Not always. BMI cannot tell muscle from fat, so athletes and very muscular people can read as overweight while carrying little fat. It also ignores where fat is stored, which matters for health risk.

No. Children and teenagers are assessed with age and sex specific percentile charts rather than the fixed adult bands, and BMI is not a valid measure during pregnancy. This calculator is intended for non-pregnant adults.

No. BMI is a starting point, not a diagnosis. It does not account for muscle, bone density, fat distribution or overall fitness. Speak with a clinician who can weigh BMI alongside waist measurement, blood work and your history before acting on it.

No. The calculation runs entirely in your browser. Your weight and height are never uploaded, logged or stored, so nothing you enter leaves your device.