Weight & Body Composition
Understand your weight, body mass, and healthy ranges with free, simple calculators. No sign-up required.
What Is BMI?
Body Mass Index (BMI) is a simple screening number calculated from your height and weight. It is used around the world by doctors, health organizations, and researchers as a rough indicator of whether a person's weight falls within a healthy range.
BMI is not a perfect measurement. It does not distinguish between muscle and fat, and it does not account for body composition, age, or ethnicity. Athletes and very muscular people may have a high BMI while being perfectly healthy. Always interpret your result alongside other factors.
BMI Categories (WHO)
- Under 18.5: Underweight
- 18.5 – 24.9: Normal weight
- 25.0 – 29.9: Overweight
- 30.0 and above: Obese
What About Ideal Weight?
The "ideal weight" is an estimate, not a single number. Different formulas (Devine, Robinson, Miller, Hamwi) produce different results. Most people have a healthy weight range of several kilograms. Our Ideal Weight Calculator shows a range for this reason.
Frequently Asked Questions
Is BMI accurate for everyone?
No. BMI is a useful screening tool for populations, but it does not work well for athletes, very muscular people, pregnant women, children, or the elderly. It is best used alongside other measurements.
Can I use these tools if I'm pregnant?
No. BMI and ideal weight ranges are not appropriate during pregnancy. Please consult your healthcare provider for guidance.
Should I make health decisions based on BMI alone?
No. BMI is one of many data points. Speak with a qualified healthcare professional before making decisions about diet, exercise, or weight management.