BMI calculator
Height and weight in, and you get your body mass index, the WHO category it falls in and the healthy weight range for your height.
How we got your number
WHOBMI is weight in kilograms divided by height in metres squared. Pounds and feet are converted first, at 1 lb = 0.453592 kg and 1 in = 2.54 cm. Categories follow the WHO classification for adults.
Healthy weight for your height
The same band in pounds is shown alongside. A range this wide is normal: BMI says nothing about what the weight is made of.
The WHO categories in full
| Category | BMI | Weight at your height |
|---|
Your own band is highlighted. Weights are worked back from the cutoffs using your height.
Lower thresholds for Asian populations
A WHO expert consultation in 2004 looked at the evidence that risk of type 2 diabetes and cardiovascular disease starts climbing at a lower BMI in many Asian populations than in European ones, at the same index value. Rather than redraw the categories, it proposed additional public health action points at 23 for increased risk and 27.5 for high risk.
Those figures are used in national guidance in countries including Singapore, China, Japan and India, and by several clinicians elsewhere for patients of South Asian, Chinese and South East Asian descent. The relevant population here is ancestry, not the country you live in.
Where BMI gets it wrong
Muscle. Muscle is denser than fat, so a trained body weighs more at the same size. Rowers, sprinters, rugby forwards and most committed lifters read overweight or obese with very low body fat. The number is not measuring what you think it is measuring.
Pregnancy. BMI is not interpreted during pregnancy. Weight gain is expected and planned, and the figure that matters to a midwife is your pre-pregnancy BMI, which sets the recommended gain for the nine months.
Older adults. People lose muscle and bone with age while keeping or gaining fat, so BMI can stay flat while body composition worsens. In over-65s a slightly higher BMI is associated with better outcomes, and some guidance moves the healthy band up to roughly 23 to 27.
Children and teenagers. The adult cutoffs do not apply at all. A growing body changes shape with age and sex, so paediatric BMI has to be read against percentile curves from the CDC or the WHO growth standards, where healthy sits between the 5th and 85th percentile for that exact age and sex. A single number cannot do that job.
Categories follow the World Health Organization classification (18.5 to 24.9 is the healthy band) and the lower Asian thresholds are shown where they apply. Nothing you enter is stored or sent anywhere. How we verify our data →
BMI FAQs
What is a healthy BMI?
The WHO healthy band runs from 18.5 to 24.9. Below 18.5 counts as underweight, 25 to 29.9 as overweight and 30 or more as obese. For people of Asian descent the risk of diabetes rises earlier, so many clinicians use 23 and 27.5 as the cut-offs instead.
Is BMI accurate for muscular people?
No. BMI only knows your height and weight, so a lean 90 kg lifter and a 90 kg desk worker of the same height get the same number. If you train hard, waist size and body fat percentage tell you more than BMI does.
What BMI is considered obese?
A BMI of 30 or above. Between 30 and 34.9 is class 1, 35 to 39.9 is class 2 and 40 or more is class 3, the range where the health risk climbs fastest.
Does BMI work for children?
Not with these thresholds. Children and teenagers are compared with others of the same age and sex on percentile charts, because a normal BMI changes as they grow. Use a paediatric chart for anyone under 18.
What should my weight be for my height?
Multiply your height in metres by itself, then by 18.5 for the bottom of the healthy range and by 24.9 for the top. At 170 cm that gives 53.5 to 72 kg, which is what the calculator shows above.
Is BMI different for men and women?
The formula and the WHO thresholds are the same. Women naturally carry more body fat at the same BMI, which is one reason BMI is a rough screening tool rather than a diagnosis.
