BMI Calculator
Calculate your BMI from height and weight in metric or imperial units, with WHO and Taiwan adult categories and a healthy weight range.
Your BMI
Enter your height and weight to see your BMI and category.
BMI is a rough screening measure based only on height and weight. It ignores muscle, body fat and age, does not apply to children and teens (use age- and sex-specific growth charts), pregnant or breastfeeding women or athletes, and is not medical advice. Talk to a doctor about any health concerns.
How to use
- Choose metric (cm, kg) or imperial (ft, in, lb).
- Enter your height and weight. Your BMI appears right away, with both the WHO and the Taiwan adult category.
- Below, see the healthy weight range for your height, an ideal weight, and how far you are from the healthy range.
FAQ
How is BMI calculated?
BMI = weight in kg ÷ (height in m)². In imperial units the tool converts with 1 lb = 0.45359237 kg and 1 in = 2.54 cm. At 170 cm and 65 kg, BMI is 65 ÷ 1.7² ≈ 22.5. The result is rounded to one decimal, and that rounded number decides the category.
What are the WHO BMI categories?
For adults: under 18.5 underweight, 18.5 to under 25 normal, 25 to under 30 pre-obese (overweight), 30 to under 35 obese class I, 35 to under 40 class II, and 40 or more class III.
Why does the tool also show a Taiwan standard?
Taiwan’s Health Promotion Administration uses lower cutoffs for adults: under 18.5 underweight, 18.5 to under 24 healthy, 24 to under 27 overweight, and 27 or more obese. Asian populations show higher metabolic risk at a lower BMI, so a BMI of 24.5 is overweight in Taiwan but normal under the WHO scale.
Who should not rely on BMI?
Children and teens under 18 need age- and sex-specific growth charts. BMI also misleads for pregnant or breastfeeding women, muscular athletes and older adults. It is a screening number, not a diagnosis; ask a doctor if you have concerns.
How is the ideal weight worked out?
The tool uses BMI 22, Taiwan’s reference value: ideal weight = 22 × (height in m)². The healthy range is the weight that gives a BMI from 18.5 up to the next category.
Is my data uploaded?
No. Your height and weight are only used in your browser and are never sent or stored.
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