BMI Calculator
Enter your height and weight to calculate your BMI (Body Mass Index), see which WHO weight category (underweight, normal weight, overweight, or obese class I–III) it falls into, and get the healthy weight range (BMI 18.5–25) for your height. Everything happens in your browser, and nothing you type is ever sent to a server. If you want to work out an age or the number of days since birth, try the Age Calculator as well.
🔒 Runs in your browser · Your data is never sent to a server
Notes
- The weight categories follow the WHO classification. BMI can misrepresent body composition for some people, such as pregnant women or those with a high muscle mass.
- BMI and the healthy weight range are statistical rules of thumb, not a medical diagnosis or personalized health advice. Talk to a doctor for guidance about your own health.
- Height and weight must be greater than 0.
Glossary
BMI (Body Mass Index)
A measure of body weight relative to height, calculated as "weight (kg) ÷ height (m)²". Because it factors out height, it's widely used as a quick way to compare weight status across people of different heights.
WHO weight categories
The World Health Organization classifies BMI under 18.5 as underweight, 18.5–24.9 as normal weight, 25–29.9 as overweight, and 30 and above as obese (split into Class I, II, and III). Some countries, including Japan, use the same cutoffs (18.5, 25, 30, 35, 40) but label the 25–30 range as an obesity grade rather than "overweight".
Healthy weight range
The range of body weight that gives a BMI between 18.5 and 25 for a given height. It's statistically associated with lower risk of weight-related health issues, and is commonly used as a target range for that height.
FAQ
How is BMI calculated?
BMI is weight in kilograms divided by height in meters squared. For example, 65 kg at 170 cm gives 65 ÷ (1.7 × 1.7) ≈ 22.5.
Do the categories differ between Japan and WHO?
This tool uses the WHO classification: under 18.5 is underweight, 18.5 to 24.9 is normal, 25 to 29.9 is overweight, and 30 or above is obese (Class I to III). Japan uses the same cutoffs, but labels 25 or above as obesity grades 1 to 4.
Can BMI alone tell me if I am healthy?
No. BMI ignores body fat and muscle mass, so muscular people may score high. For health decisions, rely on medical checkups and advice from a doctor.
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