What is BMI? How to Calculate Your Body Mass Index in Seconds

BMI — Body Mass Index — is a simple number calculated from your height and weight. It gives doctors and health professionals a quick indication of whether a person's weight might be affecting their health.

How is BMI Calculated?

BMI = weight (kg) ÷ height² (m²)

For example, if you weigh 70kg and are 1.75m tall: BMI = 70 ÷ (1.75 × 1.75) = 70 ÷ 3.0625 = 22.9

BMI Categories

• Under 18.5 — Underweight
• 18.5 – 24.9 — Normal weight ✅
• 25 – 29.9 — Overweight
• 30 – 34.9 — Obese Class I
• 35 – 39.9 — Obese Class II
• 40 and above — Obese Class III

Limitations of BMI

BMI is a useful screening tool but it has limitations. It doesn't account for muscle mass (a muscular athlete may have a high BMI without being unhealthy), bone density, age, or where fat is distributed in the body.

How to Use Our BMI Calculator

1. Choose Metric (kg/cm) or Imperial (lb/ft).
2. Enter your weight and height.
3. Click "Calculate BMI".
4. See your BMI number, category, visual scale bar, and your ideal weight range.