Free Online BMI Calculator

BMI, or body mass index, is your weight divided by your height squared. In metric, divide kilograms by meters squared: 70 kg at 1.75 m gives 70 ÷ 3.0625 = 22.9. This calculator does the same math and rounds the result to one decimal.

For adults, 18.5 to 24.9 is the normal range. This calculator uses the same cut-offs as WHO and the CDC: under 18.5 is underweight, 25 to 29.9 is overweight, and 30 or more is obese. It doesn't split obesity into further classes.

Divide your weight in pounds by your height in inches squared, then multiply by 703. At 5 ft 10 in (70 inches) and 160 lbs: 160 ÷ 4,900 × 703 = 22.96, which the calculator shows as 23. Pick imperial and enter feet and inches in separate boxes.

No. BMI is a screening number, not a diagnosis. It uses only weight and height, so muscular people can score high and people with little muscle can score low. It also ignores where fat sits. A doctor can tell you what your number means for you.

No. It applies the adult cut-offs to every result and has no age or sex box. Children and teens aged 2 to 19 are rated by BMI-for-age percentiles on growth charts, so use a child and teen calculator from the CDC or ask your pediatrician.

For adults, the cut-offs don't. The lines at 18.5, 25 and 30 are the same for men and women at every adult age, which is why this calculator asks only for weight and height. Age and sex matter for children's percentiles and for body fat, which BMI doesn't measure.

The number is rounded to one decimal, but the category comes from your exact BMI. A BMI of 24.96 shows as 25 yet stays Normal Weight, because it is still under 25. The same can happen just below 18.5 and 30. The category label is the more exact of the two.

The WHO adds two extra action points for Asian populations: 23 for increased risk and 27.5 for high risk. It keeps 18.5, 25 and 30 as the global cut-offs, and this calculator uses only those. Compare your number with the lower points yourself.

Check the units. The metric height box takes centimeters, so typing 1.75 gives a BMI over 200,000; type 175. In imperial, the inches box should hold 0 to 11, but the tool accepts more, so 5 ft 22 in counts as 6 ft 10 in.

Calculate turns on once weight and height are both above zero. In imperial, the feet box needs a number: a height typed only as inches, such as 0 ft 70 in, isn't accepted, so type 5 ft 10 in. The inches box can stay at 0.

No. The numbers you type stay in this browser tab and disappear when you reload, and they aren't stored or sent to us. The site counts page visits with Google Analytics and shows ads, but the calculator passes neither of them your measurements.