About this bmi calculator
BMI (Body Mass Index) compares your weight with your height to give a quick indication of whether you are underweight, in the healthy range, overweight or obese, using the World Health Organization categories for adults. Enter your height and weight in metric or imperial units to see your BMI and the healthy weight range for your height.
How to use it
- Choose Metric (kg, cm) or Imperial (lb, ft/in).
- Enter your weight and height.
- Your BMI, category and healthy range appear instantly.
The formula
Categories (WHO, adults): under 18.5 underweight · 18.5-24.9 normal · 25-29.9 overweight · 30+ obese
Worked example
Frequently asked questions
Is BMI accurate for everyone?
BMI is a screening guide, not a diagnosis. It can overestimate body fat in muscular athletes and underestimate it in older adults. Children and teenagers need age-specific percentile charts instead. Talk to a doctor for a full assessment.
What is a healthy BMI?
For adults, the WHO healthy range is 18.5 to 24.9. Below 18.5 is underweight, 25 to 29.9 is overweight, and 30 or above is obese.
Does BMI differ for men and women?
The adult categories are the same for men and women, although body composition differs. The calculator uses the standard WHO adult ranges.
Why show a healthy weight range as well?
A range is more practical than a single 'ideal' number — it shows the span of weights that give a BMI between 18.5 and 24.9 at your height.