Calculadora de IMC — Fórmula

How BMI Works

BMI divides your weight by your height squared. That's it. The number it produces places you into one of four categories: underweight (below 18.5), normal (18.5 to 24.9), overweight (25 to 29.9), or obese (30+). Doctors use it as a quick screening tool because it takes two seconds and needs no equipment.

The Formula

BMI = weight (kg) / height (m)^2

Or in imperial units: BMI = weight (lbs) * 703 / height (inches)^2

When to Use This

BMI is a rough population-level indicator. It works well for identifying weight-related health risk in sedentary adults who don't have unusual muscle mass. If your doctor mentions BMI at a checkup, this is the formula they're using.

What BMI Doesn't Tell You

BMI can't distinguish muscle from fat. A 5'10" person weighing 200 lbs gets a BMI of 28.7 (overweight) whether they're a competitive athlete or sedentary. It also doesn't account for where you carry weight. Belly fat around internal organs carries more health risk than fat on your hips or thighs, and BMI ignores that entirely.

For a more complete picture, consider waist-to-hip ratio, body fat percentage, or a DEXA scan.

How to Read Your Result

BMI RangeCategory Below 18.5Underweight 18.5 to 24.9Normal weight 25.0 to 29.9Overweight 30.0+Obese

These ranges were set by the WHO and apply to adults over 20. They don't apply to children, pregnant women, or highly muscular individuals.

Common Mistakes

Mixing up units. Using pounds with the metric formula (or kg with imperial) gives a meaningless number.

Applying BMI categories to children. Pediatric BMI uses age-specific percentile charts, not the adult cutoffs.

Treating BMI as a diagnosis. A high BMI isn't a disease. It's a screening number that might prompt further evaluation.