BMI Calculator – Body Mass Index (kg/m²) Chart

The calculator divides your weight in kilograms by the square of your height in metres, exactly as the World Health Organization defines the body mass index. A 70 kg person who is 1.75 m tall gets 70 ÷ 3.0625 = 22.9, which sits in the middle of the healthy band. WHO recognizes 8 classes: severe thinness below 16.0; moderate thinness 16.0–16.9; mild thinness 17.0–18.4; normal 18.5–24.9; overweight 25.0–29.9; obesity class I 30.0–34.9; class II 35.0–39.9; and class III at 40.0 or more. Your result is matched against these cut-offs, and the healthy weight range for your own height is shown in kilograms so you can set a realistic target.

1. 1

   Enter height and weight

   Type your height in centimetres and your weight in kilograms, or use the imperial fields if you prefer stones and pounds.

2. 2

   Compute kg/m²

   The tool converts height to metres, squares it, and divides your weight by it following the WHO formula.

3. 3

   Classify and advise

   Your BMI is placed into one of the 8 WHO classes and a healthy weight window for your height is calculated.

• 1

  Weigh yourself in the morning after visiting the bathroom for the most repeatable reading.

• 2

  Pair BMI with a waist measurement: 94 cm (men) or 80 cm (women) marks increased WHO risk.

• 3

  Athletes with high muscle mass should interpret a BMI of 25–27 with caution.

• Entering centimetres where metres are expected, which inflates the result by 10,000.

• Comparing a child's or teenager's BMI against adult cut-offs instead of age percentile charts.

• Treating one reading as a diagnosis instead of tracking the trend across several weeks.