BMI Calculator
Work out your body mass index in metric or imperial units, and the healthy weight range for your height.
Your BMI
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Enter your height and weight
For adults 18 and over. BMI doesn't account for muscle, age or ethnicity, so it is a starting point, not a diagnosis.
BMI categories for adults
- Under 18.5: underweight
- 18.5 to 24.9: healthy weight
- 25 to 29.9: overweight
- 30 and over: obesity
Some health services use lower thresholds for people of South Asian, Chinese and other Asian backgrounds, with overweight from 23 and obesity from 27.5. This calculator is for information only and isn't medical advice.
Frequently asked questions
How is BMI calculated?
BMI is your weight in kilograms divided by your height in metres squared. For example, 70 kg at 1.75 m is 70 ÷ (1.75 × 1.75) = 22.9. In pounds and inches, it is 703 × weight ÷ height².
What is a healthy BMI?
For adults, the World Health Organization classes a BMI 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.
Is BMI accurate?
It is a quick screening measure, not a diagnosis. It doesn't tell muscle from fat, so athletes can score as overweight, and healthy ranges differ by age and ethnicity. Waist size and a check-up with a doctor give a fuller picture.
Can children use this calculator?
No. For children and teenagers, BMI is compared with growth charts for their age and sex. Ask a doctor or use a child BMI calculator from a health service.
Are my height and weight saved?
No. The calculation happens in your browser and nothing is stored or sent anywhere.