BMI Category Calculator

Calculate your BMI and discover which weight category you fall into. Get personalized health recommendations.

1 inch = 2.54 cm

1 lb = 0.453592 kg

BMI = Weight (kg) / Height² (m) Where: • Height in meters = Height (cm) / 100 • Height² = Height (m) × Height (m) BMI Categories (WHO Classification): • Severe Underweight: BMI < 16.0 • Underweight: BMI 16.0 - 18.4 • Normal Weight: BMI 18.5 - 24.9 • Overweight: BMI 25.0 - 29.9 • Obese Class I: BMI 30.0 - 34.9 • Obese Class II: BMI 35.0 - 39.9 • Obese Class III: BMI = 40.0 Healthy Weight Range = 18.5 × Height² to 24.9 × Height²
Example: Adult patient assessment Height: 170 cm = 1.70 m Weight: 70 kg Calculation: Height² = 1.70 × 1.70 = 2.89 m² BMI = 70 / 2.89 = 24.2 Results: • BMI: 24.2 • Category: Normal Weight • Health Risk: Low Risk • Healthy Range: 53.5 - 72.0 kg (117.9 - 158.7 lbs) • Status: ? Within normal range Recommendation: Maintain current weight through balanced diet and regular exercise.

What are the BMI categories?

Underweight: <18.5, Normal weight: 18.5-24.9, Overweight: 25-29.9, Obese Class I: 30-34.9, Obese Class II: 35-39.9, Obese Class III: >=40. Based on WHO standards. Categories indicate health risk levels but don't account for muscle mass, age, or ethnicity.

What is a healthy BMI range?

For most adults: 18.5-24.9 is considered normal/healthy. This range is associated with lowest mortality risk. However, optimal BMI varies by age (higher OK for seniors), ethnicity (Asian standards: 18.5-23), and muscle mass (athletes may be "overweight" but healthy).

What are the health risks for different BMI categories?

Underweight (<18.5): malnutrition, weakened immune system, osteoporosis. Overweight (25-29.9): increased risk diabetes, heart disease, sleep apnea. Obese (30+): significantly higher risk of type 2 diabetes, heart disease, stroke, certain cancers, joint problems, reduced life expectancy.

How can I move to a healthier BMI category?

To lose weight: calorie deficit (eat less + move more), aim for 1-2 lbs/week loss, strength training to preserve muscle, sustainable lifestyle changes. To gain weight: calorie surplus with nutritious foods, resistance training, medical evaluation if underweight. Calculate target weight for desired BMI.

Is BMI accurate for everyone?

BMI limitations: doesn't distinguish muscle vs fat (bodybuilders may be "obese"), doesn't account for body composition, age, sex, ethnicity differences. Better for populations than individuals. Consider waist circumference, body fat %, blood markers. Consult doctor for personalized assessment.