BMI calculator

How it works

Enter your weight and height. Body mass index compares weight with height to give a quick screening number for adults.

The formula

BMI = weight (kg) ÷ height (m)². Ranges for adults: under 18.5 underweight, 18.5–24.9 healthy, 25–29.9 overweight, 30 and above obesity.

Worked example

70 kg and 1.75 m: 70 ÷ (1.75 × 1.75) = 70 ÷ 3.0625 ≈ 22.9, which is in the healthy range.

Good to know

• BMI does not separate muscle from fat, so athletes can score high.
• Children and teenagers use age-based percentiles, not these adult ranges.
• It is a screening tool, not a diagnosis; talk to a doctor about your health.