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BMI calculator

Find your Body Mass Index (BMI) from your height and weight, see whether it is in the healthy range by the WHO categories, and the weight range that would be healthy for your height.

1You

Your weight — switch the unit to kg or lb.

Your height — enter in metres, centimetres or feet and inches.

Your results

Your results appear here

Type your measurements in the empty boxes. Still needed:

  • Weight
  • Height
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How to calculate your BMI

  1. 1Enter your weight (kg or lb).
  2. 2Enter your height (m, cm or feet and inches).
  3. 3Read your BMI, its category, and the healthy weight range for your height.

BMI formula and categories

  1. 01BMI = weight (kg) ÷ height (m)²
  2. 02Underweight < 18.5 · Healthy 18.5–24.9 · Overweight 25–29.9 · Obese ≥ 30
  3. 03Healthy weight range = 18.5 to 24.9 × height (m)²

Body Mass Index is your weight in kilograms divided by the square of your height in metres. It is a quick screen for whether your weight is in a healthy range for your height, used by the World Health Organization and doctors worldwide.

The WHO bands are the same for adult men and women: under 18.5 is underweight, 18.5 to 24.9 healthy, 25 to 29.9 overweight, and 30 or more obese. Turning the healthy band back into weights gives the range shown — the weights that would put your BMI between 18.5 and 24.9.

BMI is only a guide. It doesn't tell muscle from fat, so very muscular people can read high, and it is less accurate for the very short, the elderly, and pregnant women. Use it alongside, not instead of, a doctor's advice.

BMI calculation example

At 70 kg and 1.75 m, your BMI is 22.9.

A healthy weight for that height is about 56.7 kg to 76.3 kg.

Good to know

  • BMI is a screen, not a diagnosis — very muscular people can read high despite low body fat.
  • Waist size is a useful second check: more belly fat raises health risks even at a normal BMI.
  • Track the trend over months rather than day-to-day weight, which swings with water and food.

BMI calculator — common questions

How is BMI calculated?

BMI is your weight in kilograms divided by your height in metres squared. For example 70 kg ÷ (1.75 m)² = 22.9.

What is a healthy BMI?

The WHO healthy range is 18.5 to 24.9. Below that is underweight; 25–29.9 is overweight; 30 or more is obese.

Is BMI accurate?

It's a useful general screen but doesn't distinguish muscle from fat, so athletes may read high. It's less accurate for children, the elderly and pregnant women.

What is a healthy weight for my height?

The weights that give a BMI of 18.5 to 24.9. This calculator shows that range for the height you enter.

Sources

Formulas last reviewed: September 30, 2026 ·How we check our formulas

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