BMI (Body Mass Index) is a simple number calculated from your weight and height. It is used by doctors, insurance companies, and health organizations as a quick screening tool for weight categories. It is not a perfect measure, but it is a useful starting point.

The Formula: BMI = weight (kg) ÷ height² (m²). For imperial units: BMI = weight (lbs) × 703 ÷ height² (in²). Example: A person who is 175cm (1.75m) tall and weighs 70kg has a BMI of 70 ÷ (1.75 × 1.75) = 70 ÷ 3.0625 = 22.9.

BMI Categories:

• Underweight: Below 18.5

• Normal weight: 18.5 – 24.9

• Overweight: 25.0 – 29.9

• Obese: 30.0 and above

What I Tested: I used the [BMI Calculator](/calculator-tools/bmi-calculator) with three different inputs.

• Height: 175cm, Weight: 65kg → BMI: 21.2 (Normal weight). Correct.

• Height: 180cm, Weight: 95kg → BMI: 29.3 (Overweight). Correct.

• Height: 160cm, Weight: 50kg → BMI: 19.5 (Normal weight). Correct.

The calculator shows the BMI number and the corresponding category instantly.

Step-by-Step: (1) Open the [BMI Calculator](/calculator-tools/bmi-calculator). (2) Enter your height in centimeters (or feet/inches). (3) Enter your weight in kilograms (or pounds). (4) Click 'Calculate'. (5) Read your BMI value and weight category.

One Important Limitation: BMI does not distinguish between muscle and fat. A muscular athlete may have a BMI of 28 (overweight) with very low body fat. BMI also does not account for bone density, body composition, or fat distribution. It is a screening tool, not a diagnostic. For a complete health assessment, consult a healthcare professional.

Common Mistake: Using BMI as the sole health indicator. BMI is one data point among many. Waist circumference, blood pressure, blood sugar, cholesterol levels, and overall fitness level are equally or more important. Do not panic over a single BMI number.

Privacy: Your weight and height are processed entirely in your browser. No data is sent to any server.

Next Step: If you are tracking health metrics regularly, also check your ideal weight using our related calculator tools.

How to Calculate Your BMI and What the Number Actually Means