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Free tool · BMI

BMI calculator for adults

Check your body mass index in metric or imperial units, see your weight category and the healthy weight range for your height.

Your measurements

Units
cm
kg

Your BMI

22.9Healthy weight

Healthy weight for your height
56.7 kg – 76.3 kg
Your weight
70 kg
  • UnderweightBelow 18.5
  • Healthy weight18.5 – 24.9
  • Overweight25 – 29.9
  • Obesity (class I)30 – 34.9
  • Obesity (class II)35 – 39.9
  • Obesity (class III)40 and above

BMI is a screening measure for adults aged 18 and over. It doesn't account for muscle mass, age, sex or ethnicity, and some people of Black African, African-Caribbean and Asian heritage have higher health risks at lower BMIs. This is not medical advice; speak to a doctor or pharmacist about your health.

How it works

What your BMI tells you

Body mass index compares your weight with your height: BMI = weight (kg) ÷ height (m)². The result is placed into the World Health Organization's adult categories, from underweight to obesity class III.

The healthy weight range shows the weights that would give you a BMI of 18.5 to 24.9 at your height, a helpful target if you're planning changes to diet or activity.

BMI is a quick screening tool, not a diagnosis. Waist measurement, activity levels and family history matter too. If you're concerned about your weight, speak to a GP or pharmacist.

Sources

Private by design

Every calculation runs in your browser. Nothing you type is sent to us or stored.

FAQ

Common questions

What is a healthy BMI?

For most adults, a BMI between 18.5 and 24.9 is considered a healthy weight. Below 18.5 is underweight, 25 to 29.9 is overweight, and 30 or above is obesity.

How is BMI calculated?

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

Is BMI accurate for everyone?

No. BMI doesn't distinguish muscle from fat, so very muscular people can have a high BMI. It also doesn't account for age, sex or ethnicity. It is a useful starting point, not a diagnosis.

Are BMI thresholds different for some ethnic groups?

Yes. Health risks such as type 2 diabetes start at a lower BMI for people of Black African, African-Caribbean, South Asian and Chinese heritage. The NHS suggests a BMI of 23 or more may indicate an increased risk for these groups.

Can children use this BMI calculator?

No. Children's BMI has to be compared against growth charts for their age and sex. This calculator is for adults aged 18 and over.

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