Calculate your body mass index and WHO category, with the healthy weight range for your height.
kg
lb
cm
ft
in
Enter the values to see the result here.
For general information, not medical advice. Talk to a doctor before making health decisions.
Formula
BMI=height (m)2weight (kg)
For imperial inputs the tool first converts pounds to kilograms (× 0.45359237) and feet and inches to centimetres (× 2.54). WHO adult categories: under 18.5 underweight, 18.5 to 24.9 healthy, 25 to 29.9 overweight, 30 to 34.9 obesity class 1, 35 to 39.9 class 2, 40 and above class 3.
The healthy range for your height is 18.5h2 to 24.9h2 with h in metres.
Worked example
A person weighs 70 kg and is 175 cm tall.
Height in metres: 1.75; squared: 3.0625.
BMI: 70/3.0625=22.9, in the healthy band.
Healthy range at this height: 18.5×3.0625=56.7 kg to 24.9×3.0625=76.3 kg.
The same 70 kg at 160 cm gives 70/2.56=27.3, which is in the overweight band, so height matters as much as weight.
Common mistakes
Entering height in centimetres where the tool expects feet and inches, or vice versa. Pick the unit system first.
Using pounds with the metric formula. The imperial option converts for you.
Treating the boundary values as sharp. A BMI of 24.9 and 25.1 are not meaningfully different.
Applying adult cut-offs to under-18s, pregnant women or people with a lot of muscle.
Frequently asked questions
Is BMI accurate for athletes?
Often not. Muscle is denser than fat, so a muscular person can score "overweight" with low body fat. Waist size or a body fat estimate gives a better picture.
Do the same BMI cut-offs apply to all ethnic groups?
The WHO suggests lower action points for many Asian populations (overweight from about 23) because health risks rise at lower BMI. Talk to a clinician about what applies to you.
Can I use BMI for children?
No. Children and teenagers are assessed with age- and sex-specific growth charts. This tool is for adults aged 18 and over.
Does a healthy BMI mean I am healthy?
Not by itself. Diet, activity, blood pressure and blood tests matter as much. BMI is a screening number, not a diagnosis.