How to use the BMI Calculator
- 1
Choose metric (kg, cm) or imperial (lb, ft, in) units.
- 2
Enter your height and weight.
- 3
Read your BMI, its category and the healthy weight range for your height on the colour scale.
Features & benefits
Metric & imperial
Switch units at any time; values are converted automatically.
WHO categories
Underweight, healthy weight, overweight and obesity classes I–III.
Healthy range
Shows the weight range that corresponds to a BMI of 18.5–24.9 at your height.
Visual scale
A colour-coded bar shows where your result sits.
Understanding BMI
BMI equals weight in kilograms divided by height in metres squared. For imperial units, the formula is 703 × weight in pounds ÷ height in inches squared. For most adults, a BMI from 18.5 to 24.9 is classified as a healthy weight.
BMI is a population-level screening tool and does not measure body fat directly. Muscular athletes can have a high BMI while being very healthy, and it may be less accurate for older adults, during pregnancy, and for some ethnic groups. Children and teenagers need age- and sex-specific percentiles instead. Always discuss your health with a qualified professional.
Frequently asked questions
Is BMI accurate for everyone?
No. It doesn't distinguish muscle from fat or account for body shape. Use it as a starting point, not a diagnosis.
Can children use this calculator?
This calculator uses adult categories. For people under 20, BMI must be interpreted with age- and sex-specific growth charts.
What is a healthy BMI?
The WHO defines 18.5–24.9 as the healthy range for adults.