Calculate your Body Mass Index from weight and height in metric or imperial units. See your WHO category, your healthy weight range and an age-based reference.
How to use the BMI Calculator
Choose metric or imperial units.
Enter your weight and height, and optionally your age for an age-based range.
Read your BMI, category and the healthy weight range for your height.
Frequently asked questions
BMI is your weight in kilograms divided by the square of your height in metres (kg/m²). For example, 70 kg at 1.75 m gives a BMI of about 22.9.
The WHO defines: under 18.5 underweight, 18.5 to 24.9 normal weight, 25 to 29.9 overweight, and 30 or more obesity, which is split into classes I, II and III.
No. BMI ignores muscle mass, build, age and fat distribution, so athletes and older adults can be misclassified. Treat it as a rough screening guide, not a diagnosis.
The optimal BMI tends to rise slightly with age. If you enter your age, the tool shows the commonly used age-adjusted normal range for adults alongside the standard WHO range.
The BMI calculator works out your Body Mass Index from your weight and height and places it in the World Health Organization weight categories. It also shows the weight range that would keep you in the normal category for your height.
It supports metric and imperial units and an optional age-based reference range. BMI is a quick screening tool for adults; it does not replace advice from a doctor.
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