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BMI (Body Mass Index) is the most widely used screening tool for weight categories. While it has limitations, it provides a quick, standardized way to assess whether your weight is in a healthy range relative to your height.
BMI doesn't distinguish between muscle and fat. Athletes with high muscle mass may be classified as "overweight" despite being very fit. Similarly, older adults who've lost muscle may have a "normal" BMI but carry excess body fat ("skinny fat"). For better assessment, combine BMI with waist circumference and body fat percentage.
For ages 2-19, BMI is interpreted differently — it's compared to age and gender percentiles rather than fixed numbers. A child at the 85th percentile has a higher BMI than 85% of children their age and gender. Consult a pediatrician for children's weight assessment.
BMI (Body Mass Index) = weight (kg) / height (m)². It estimates body fatness as a screening tool for weight problems in adults.
Underweight: below 18.5. Normal: 18.5–24.9. Overweight: 25–29.9. Obese I: 30–34.9. Obese II: 35–39.9. Obese III: 40+.
Useful for populations but has individual limitations. Doesn't distinguish muscle from fat. Best used alongside waist circumference and body fat percentage.
18.5–24.9 is normal. Some research suggests lowest mortality at BMI 22-25. Older adults (65+) may benefit from slightly higher (25-27).
Metric: weight (kg) / height (m)². Imperial: weight (lbs) / height (in)² × 703. Example: 175 lbs, 5'10\": 175 / 4900 × 703 = 25.1.
For BMI 18.5-24.9: 5'0\" = 94-127 lbs, 5'5\" = 113-150 lbs, 5'10\" = 132-174 lbs, 6'0\" = 144-189 lbs.
Better: body fat % (DEXA/calipers), waist-to-height ratio, waist circumference (men < 40\", women < 35\"), waist-to-hip ratio.
BMI can't tell muscle from fat. A 6'2\" football player at 240 lbs with 12% body fat has BMI 30.7 ('obese'), but is extremely fit.