BMI
Body mass index in metric or imperial, with a healthy range.
About BMI
BMI Calculator works out your body mass index from your weight and height, in metric or imperial units, and shows the healthy weight range for someone of your height. BMI is weight in kilograms divided by height in metres squared. It is a screening number used to sort populations into broad categories, not a measure of health for any individual — it cannot tell muscle from fat, and it was never designed to.
How to use it
- Choose metric (kg and cm) or imperial (lb and inches).
- Enter your weight and height.
- Read your BMI, its category, and the healthy weight range for your height.
Questions
What are the BMI categories?
Under 18.5 is underweight, 18.5 to 24.9 is normal, 25 to 29.9 is overweight, and 30 or above is obese. These thresholds come from WHO guidance for adults.
Why is BMI criticised?
Because it only knows your weight and height. A muscular athlete often scores "overweight" while someone with little muscle can score "normal" while carrying unhealthy body fat. It also does not account for age, sex, or where fat is distributed — and abdominal fat matters far more than total weight.
Does BMI work for everyone?
No. It is not valid for children, pregnant women, or people with unusual muscle mass. Several health bodies also recommend lower thresholds for people of South Asian descent, who face higher risk at the same BMI.
What is a better measure?
Waist circumference and waist-to-height ratio predict health risk better than BMI. Keeping your waist under half your height is a useful rule of thumb. The Body Fat tool in the Health Hub estimates composition from tape measurements.
BMI is free and runs entirely in your browser. No account, no upload, no watermark, no limit on use.