Calculate your Body Mass Index instantly. See your BMI category, ideal weight range for your height, and where you fall on the BMI scale. Supports metric and imperial units.
| Category | BMI Range | Your Weight Range |
|---|
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Body Mass Index is the most widely used screening tool for weight classification. Developed by Belgian mathematician Adolphe Quetelet in 1832, BMI uses a simple ratio of weight to height to categorize adults as underweight, normal, overweight, or obese. It is used by doctors, insurance companies, and public health researchers worldwide. This guide explains how BMI works, where it falls short, and how to use it properly.
| Category | BMI Range | Health Risk |
|---|---|---|
| Underweight | < 18.5 | Increased (nutritional deficiency) |
| Normal Weight | 18.5 – 24.9 | Lowest risk |
| Overweight | 25.0 – 29.9 | Mildly increased |
| Obese Class I | 30.0 – 34.9 | Moderate |
| Obese Class II | 35.0 – 39.9 | Severe |
| Obese Class III | ≥ 40 | Very severe |
Scenario 1: Average Adult Male. James is 5’10” (178 cm) and 185 lbs (84 kg). BMI: 84 / (1.78)² = 26.5 — Overweight. His ideal weight range is 131–174 lbs (59–79 kg). He needs to lose about 11 lbs to reach normal BMI. Use our Calorie Deficit Calculator to plan his approach.
Scenario 2: Petite Woman. Maria is 5’2” (157 cm) and 115 lbs (52 kg). BMI: 52 / (1.57)² = 21.1 — Normal Weight. She is squarely in the healthy range. Her ideal range is 91–123 lbs (41–56 kg). Use our TDEE Calculator to maintain her current weight with proper nutrition.
Scenario 3: Muscular Athlete. David is 6’0” (183 cm), 220 lbs (100 kg), lifts weights 5x/week, and has visible abs. BMI: 100 / (1.83)² = 29.9 — Overweight. But David has ~12% body fat. BMI is misleading here because muscle weighs more than fat. Use our Body Fat Calculator instead.
Scenario 4: Underweight Concern. Sarah is 5’6” (168 cm) and 105 lbs (48 kg). BMI: 48 / (1.68)² = 17.0 — Underweight. She needs to gain 7+ lbs to reach the normal range minimum. Being underweight increases risk of nutritional deficiency and weakened immunity. Use our TDEE Calculator to calculate a calorie surplus for healthy weight gain.
💡 Key insight: BMI is a screening tool, not a diagnostic tool. It does not measure body fat directly and does not account for muscle mass, bone density, age, sex, or ethnicity. An athlete with 10% body fat and a BMI of 28 is healthier than a sedentary person with 35% body fat and a BMI of 26. Always pair BMI with other measurements like waist circumference and body fat percentage.
| < 18.5 | Underweight |
| 18.5 – 24.9 | Normal |
| 25 – 29.9 | Overweight |
| 30 – 34.9 | Obese I |
| 35+ | Obese II+ |