BMI Calculator
Calculate Body Mass Index from weight and height, in imperial or metric.
Pick units, type weight and height, get BMI plus the standard category label.
Example: 160 lb at 5'10" (70 in) = BMI 23.0 (normal range).
What BMI is and is not
Body Mass Index is a quick screening number derived from weight and height. The formula is weight in kilograms divided by height in meters squared (or, for imperial: weight in pounds divided by height in inches squared, multiplied by 703). It is widely used because it is easy to calculate and correlates with body fat in large populations.
BMI does NOT measure body fat directly. It does not distinguish muscle from fat. A muscular athlete may have a "high" BMI but very low body fat. An older person with low muscle mass may have a "normal" BMI but high body fat. Use BMI as a starting point for conversation with a doctor, not as a verdict.
The standard adult categories
- Under 18.5: Underweight
- 18.5 - 24.9: Normal weight
- 25.0 - 29.9: Overweight
- 30.0 - 34.9: Obese (class I)
- 35.0 - 39.9: Obese (class II)
- 40.0+: Obese (class III)
These categories apply to adults 20 and older. Children and teens use age- and sex-specific BMI-for-age percentiles instead. For a more complete picture, talk to your healthcare provider about body composition assessment (DEXA scan, BodPod, or skinfold measurements).
Informational only. This calculator is not medical advice and does not diagnose, treat, or prevent any condition. Always consult a qualified healthcare provider for medical decisions.