BMI Calculator

Frequently asked questions

• How is BMI calculated?

  BMI = weight in kilograms ÷ (height in metres)². This page takes height in centimetres and divides it by 100 first. For 70 kg and 175 cm, height is 1.75 m, and BMI is 70 ÷ (1.75 × 1.75) = 22.86.

• What do the BMI categories mean?

  Under 18.5 is Underweight. From 18.5 up to, but not including, 25 is Normal. From 25 up to, but not including, 30 is Overweight. 30 and above is Obese. These are the adult bands this calculator uses.

• Is BMI a diagnosis?

  No. BMI is a screening number from height and weight only. It does not measure body fat, muscle, bone, or health conditions. A doctor should interpret it with your age, waist, and medical history.

• Does this BMI calculator work for children?

  This tool uses adult cut-offs. Children’s BMI is judged against age and sex charts, not the 18.5 and 25 bands used here. Do not use this result alone for a child or teenager.

• Why can an athletic person have a high BMI?

  Muscle weighs more than fat for the same body size. A muscular person can land in Overweight or Obese without having a high body-fat level. BMI cannot tell muscle and fat apart.

• Why does the circle stop at 40?

  The ring is a visual scale filled at a BMI of 40. The BMI number itself is not capped. A result above 40 still shows in full and is categorised as Obese.