BMI Calculator
Enter your height and weight. Your BMI updates as you type, calculated entirely on your device.
Your measurements
- Under 18.5 underweight
- 18.5–24.9 healthy
- 25–29.9 overweight
- 30+ obesity (classes I–III)
BMI is a quick screening measure for adults aged 18 and over. It does not tell muscle from fat, and it is not used this way for children and teens, who are assessed with age- and sex-specific percentile charts. For advice about your health, talk to a doctor.
How BMI is calculated
Body mass index is your weight divided by the square of your height: BMI = weight (kg) ÷ height (m)². In imperial units the same formula is 703 × weight (lb) ÷ height (in)². For example, 70 kg at 1.75 m gives 70 ÷ 3.0625 = 22.9.
The healthy weight range shown is the weight that gives a BMI from 18.5 to 24.9 at your height. BMI Prime is your BMI divided by 25, the upper limit of the healthy range, so 1.00 sits exactly at that limit.
WHO adult categories
Below 18.5 is underweight (16–16.9 moderate, under 16 severe), 18.5–24.9 is a healthy weight, 25–29.9 is overweight, and 30 or more is obesity: class I (30–34.9), class II (35–39.9) and class III (40 and over). Some health bodies, including in India and other parts of Asia, use lower action points (for example 23 for overweight) because health risks can begin at a lower BMI.
FAQ
Why might BMI be misleading for me?
BMI uses only height and weight. Very muscular people can have a high BMI without excess fat, and older adults can have a normal BMI while carrying more body fat. Waist size and other checks give a fuller picture.
Is my data saved?
No. The calculation runs in your browser with WebAssembly. Your height and weight are never sent or stored; only your preferred unit system is remembered on this device.