BMI Calculator
Calculate your Body Mass Index (BMI) using imperial or metric measurements.
Enter your height and weight above to see your BMI.
< 18.5 — Underweight
18.5–24.9 — Normal
25–29.9 — Overweight
≥ 30 — Obese
BMI is a screening tool, not a diagnostic. Consult a healthcare provider for a full assessment.
How Is BMI Calculated?
BMI divides your weight by the square of your height. The formula differs by unit system:
Metric: BMI = weight (kg) ÷ height² (m)
Imperial: BMI = (weight (lbs) × 703) ÷ height² (in)
Example — 5′9″, 170 lbs:
- Height in inches = 69 in
- BMI = (170 × 703) ÷ (69²) = 119,510 ÷ 4,761 = 25.1 → Overweight
Metric shortcut: Convert height to metres first (e.g. 175 cm = 1.75 m), then: 70 ÷ (1.75 × 1.75) = 70 ÷ 3.0625 = BMI 22.9 (Normal).
Frequently Asked Questions
What is BMI and how is it calculated?▼
BMI (Body Mass Index) is calculated by dividing your weight in kilograms by your height in meters squared. In imperial units: BMI = (weight in lbs × 703) ÷ (height in inches)². It provides a simple numeric measure of body size.
What is a healthy BMI range for adults?▼
For adults, a BMI between 18.5 and 24.9 is considered normal weight. Under 18.5 is underweight, 25–29.9 is overweight, and 30 or above is classified as obese.
Is BMI accurate for women over 50?▼
BMI is less accurate for women over 50 because it does not account for changes in muscle mass and fat distribution that come with age and menopause. A healthcare provider may recommend waist circumference or body fat percentage for a more complete picture.
What BMI is considered obese?▼
A BMI of 30 or higher is classified as obese — Class 1 (30–34.9), Class 2 (35–39.9), and Class 3 or severe obesity (40 and above).
Can athletes have a high BMI and still be healthy?▼
Yes. Athletes with high muscle mass often have a BMI in the overweight range despite having very low body fat. This is a well-known limitation of BMI.
How do I lower my BMI?▼
Lowering BMI typically involves reducing caloric intake and increasing physical activity. Aim for 150+ minutes of moderate exercise per week and a balanced diet. Consult a healthcare provider before starting.