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BMI calculator for adults

Work out your body mass index from your height and weight, in centimetres and kilograms or feet and pounds. You will see your BMI, its World Health Organization category, and the weight range that counts as healthy for your height. Nothing you enter is saved.

Quick answer

BMI is your weight in kilograms divided by the square of your height in metres. For adults, the World Health Organization treats under 18.5 as underweight, 18.5 to 24.9 as a healthy weight, 25 to 29.9 as overweight and 30 or more as obesity. Enter your height and weight below, in metric or imperial units, to see your BMI and your healthy weight range.

Enter your height and weight to see your BMI.

  • Underweight< 18.5
  • Healthy weight18.5 – 24.9
  • Overweight25 – 29.9
  • Obesity class I30 – 34.9
  • Obesity class II35 – 39.9
  • Obesity class III≥ 40

For adults aged 18 and over. BMI is a screening measure, not a diagnosis: it does not account for muscle, age, ethnicity or pregnancy. Talk to a doctor about your health.

How to use the BMI Calculator

  1. Choose metric or imperial units.
  2. Enter your height and your weight.
  3. Read your BMI, where it sits on the scale, and the healthy weight range for your height.

How BMI is calculated

Body mass index is your weight in kilograms divided by the square of your height in metres. Someone who is 1.75 m tall and weighs 70 kg has a BMI of 70 ÷ (1.75 × 1.75) = 22.9. If you use pounds and inches, the calculator converts them first, so the result is the same.

What the BMI categories mean

The World Health Organization groups adult BMI into bands. Below 18.5 is underweight, 18.5 to 24.9 is a healthy weight, 25 to 29.9 is overweight and 30 or more is obesity, which is split into class I (30 to 34.9), class II (35 to 39.9) and class III (40 and above). Higher bands are linked with a greater risk of conditions such as type 2 diabetes, high blood pressure and heart disease, which are common health concerns across the Gulf.

The limits of BMI

BMI is a quick screening number, not a measure of body fat or health. A muscular athlete can have a high BMI while being very fit, and an older adult can have a normal BMI with little muscle. Some health bodies use lower cut-offs for people of South Asian and other Asian backgrounds, because health risks start at a lower BMI. BMI is not used during pregnancy, and children and teenagers are assessed with age-and-sex growth charts instead. Waist size and a check-up with a doctor give a fuller picture.

Using your healthy weight range

The healthy range shown is the weight that gives a BMI between 18.5 and 24.9 at your height. Treat it as a broad guide. If you are outside it, small steady changes in eating, activity and sleep matter more than reaching a single number, and a doctor or dietitian can help you set a realistic goal.

Frequently asked questions

What is a healthy BMI?

For most adults a BMI of 18.5 to 24.9 is considered a healthy weight by the World Health Organization.

Is BMI accurate for athletes?

Not always. BMI cannot tell muscle from fat, so people with a lot of muscle may show as overweight even when their body fat is low.

Can children use this calculator?

No. It is for adults aged 18 and over. Children and teenagers are assessed with growth charts that take age and sex into account.

How do I calculate BMI in pounds and feet?

Choose Imperial, then enter your height in feet and inches and your weight in pounds. The calculator converts them to metric and uses the same formula.

Is my height and weight saved?

No. The calculation runs in your browser and nothing you enter is stored or sent.

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