Calculate adult Body Mass Index (ages 20+), CDC weight status category, bidirectional U.S. Customary and Metric conversions, and height-based reference weight screening range.
| CDC Screening Category | BMI Range (kg/m²) |
|---|---|
| Underweight | Below 18.5 |
| Healthy Weight (Reference Range) | 18.5 – 24.9 |
| Overweight | 25.0 – 29.9 |
| Obesity (Class 1) | 30.0 – 34.9 |
| Obesity (Class 2) | 35.0 – 39.9 |
| Obesity (Class 3 — Severe) | 40.0 or higher |
Body Mass Index (BMI) is a person's weight in kilograms divided by the square of height in meters—or 703 times weight in pounds divided by the square of height in inches. For adults aged 20 and older, the U.S. CDC classifies BMI into Underweight (<18.5), Healthy Weight (18.5–24.9), Overweight (25.0–29.9), and Obesity (30.0+, subdivided into Classes 1, 2, and 3).
In U.S. Customary units, total height in inches is h = (feet × 12) + inches, and BMI = 703 × weight_lb / h². In Metric units, height in meters is m = cm / 100, and BMI = weight_kg / m². The height-based reference weight screening range calculates the exact weights corresponding to BMI 18.5 and BMI 24.9 for the entered height in both pounds and kilograms.
An adult aged 20+ measures 5 feet 9 inches tall (69 inches total, or 175.3 cm) and weighs 160 pounds (72.6 kg).
BMI = 703 × 160 / (69²) = 112,480 / 4,761 = 23.6 kg/m² (CDC Category: Healthy Weight, 18.5–24.9). Reference screening weight range for 5'9": 125.3 lb – 168.6 lb (56.8 kg – 76.5 kg).
An adult measures 170 cm tall (5 ft 6.9 in) and weighs 82 kg (180.8 lb).
BMI = 82 / (1.70²) = 82 / 2.89 = 28.4 kg/m² (CDC Category: Overweight, 25.0–29.9). Reference screening weight range for 170 cm: 53.5 kg – 72.0 kg (117.9 lb – 158.6 lb); 10.0 kg (22.2 lb) above the BMI 24.9 reference threshold.
In Metric units, divide weight in kilograms by height in meters squared: BMI = kg / m². In U.S. Customary units, convert feet and inches into total inches, square that number, divide weight in pounds by squared inches, and multiply by the conversion factor 703: BMI = 703 × lb / in².
According to the U.S. Centers for Disease Control and Prevention (CDC), body composition changes as children and teenagers grow, and differs between boys and girls. For ages 2 through 19, BMI must be interpreted relative to others of the same age and sex using CDC BMI-for-age percentile growth charts rather than fixed adult cutoffs.
No. The CDC and NHLBI emphasize that BMI is a screening measure based solely on weight and height. It does not distinguish between lean muscle mass and adipose tissue, nor does it account for waist circumference, bone density, or metabolic health markers.
It shows the mathematical weight interval that yields a BMI between 18.5 and 24.9 for your specific height. It serves as a general statistical screening reference and should not be interpreted as a universally ideal weight for every person.