Free BMI Calculator
Calculate your Body Mass Index instantly. Get your BMI category, healthy weight range, and actionable insights — no signup required.
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What Is BMI and How Is It Calculated?
Body Mass Index (BMI) is a simple screening metric that uses your weight and height to estimate body fat. It's widely used by healthcare professionals, including dietitians, as a quick assessment tool during client consultations. While BMI doesn't measure body fat directly, it correlates with more direct measures and helps identify weight categories that may lead to health concerns.
The BMI Formula
BMI uses a straightforward ratio of weight to height squared, defined by the World Health Organization (WHO).
Metric:
BMI = weight (kg) ÷ height (m)²
Imperial:
BMI = 703 × weight (lbs) ÷ height (in)²
WHO BMI Categories
The WHO defines four primary BMI classifications for adults aged 20 and over.
Underweight: BMI < 18.5
Normal weight: BMI 18.5 – 24.9
Overweight: BMI 25 – 29.9
Obese: BMI ≥ 30
Your Healthy Weight Range
A “normal” BMI falls between 18.5 and 24.9. This calculator shows you the exact weight range for your height that corresponds to a healthy BMI, giving you a concrete target rather than an abstract number.
BMI Limitations
BMI does not distinguish between muscle and fat mass. Athletes and highly muscular individuals may have a high BMI despite low body fat. For a more complete picture, dietitians often combine BMI with waist circumference, body composition analysis, and clinical assessment.
Want to go deeper?
BMI tells you where you are. Our TDEE calculator tells you what to do about it — with personalized daily calories and macro targets for weight loss, maintenance, or muscle gain.
Try the TDEE Calculator →Disclaimer
BMI is a screening tool, not a diagnostic measure. It does not account for age, sex, ethnicity, muscle mass, or bone density. For personalized health assessments and nutrition advice, consult a licensed dietitian or healthcare professional.