What is BMI?
Body Mass Index (BMI) is a simple number calculated from your weight and height. It is widely used as a screening tool to identify possible weight categories for adults. The formula is weight in kilograms divided by height in meters squared.
BMI categories for adults
- Below 18.5: Underweight
- 18.5 – 24.9: Healthy weight
- 25 – 29.9: Overweight
- 30 and above: Obesity
Limitations of BMI
BMI does not measure body fat directly. Athletes with high muscle mass may have a high BMI without excess fat, and older adults may have a normal BMI with low muscle mass. It also does not show where fat is distributed. For a complete picture, health professionals also consider waist circumference, diet, activity level and medical history.
Next steps
If your result is outside the healthy range, consider speaking with a doctor or registered dietitian. Small, sustainable habits such as regular movement, balanced meals and good sleep are more effective than extreme diets.
Frequently asked questions
Is BMI accurate for everyone?
No. It is a screening tool and does not account for muscle mass, age, sex or body composition.
Can children use this calculator?
No. Children and teens use age- and sex-specific percentile charts instead of adult BMI categories.
Does this give medical advice?
No. It is for information only. Consult a healthcare professional for personal guidance.