Adult BMI Calculator — US Units (lb/in)
Instant Body Mass Index calculation with US imperial units by default. Enter your weight and height to see your WHO/CDC category update in real time.
How This Calculator Works
Type your weight in pounds and your height in inches into the fields above. The calculator recalculates instantly with every keystroke — there is no "Calculate" button. Your BMI value and category update in real time.
BMI Formula (US Imperial)
For imperial units, BMI is computed as:
BMI = 703 × weightlb / heightin²
The constant 703 converts pound-per-square-inch into the standard kilogram-per-square-meter scale used by WHO and CDC, so imperial and metric inputs yield numerically identical BMI values.
BMI Formula (Metric)
BMI = weightkg / heightm². If you enter centimeters, the calculator divides by 100 first.
WHO / CDC Adult BMI Classification
| Category | BMI Range | Color |
|---|---|---|
| Underweight | Below 18.5 | Orange |
| Normal weight | 18.5 – 24.9 | Green |
| Overweight | 25.0 – 29.9 | Yellow |
| Obese | 30.0 and above | Red |
The four-category scheme is taken from the WHO 2000 report Obesity: Preventing and Managing the Global Epidemic and adopted by the CDC for adult populations aged 20 and over.
Interpreting Your BMI Result
BMI is a population-level screening ratio, not a diagnostic test. It is derived only from total weight and height and does not distinguish lean mass from adipose tissue. Two people with identical BMI values can have substantially different body compositions depending on muscularity, bone density, age, sex, and ethnicity. For individuals with high muscle mass, BMI may overestimate body fat. For older adults with reduced lean mass, BMI may underestimate adiposity. Always consult a qualified healthcare provider for medical concerns.