BMI Calculator
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How to use BMI Calculator
- Enter your weight in kilograms and height in centimeters.
- Read your BMI and category.
- Remember it is a screening guide, not a diagnosis.
Common uses
- Getting a quick weight-status estimate.
- Tracking changes over time.
- Preparing for a conversation with a health professional.
About this tool
Body mass index is weight in kilograms divided by height in metres squared. This calculator shows your BMI and the standard adult category (under 18.5 underweight, 18.5 to 24.9 normal, 25 to 29.9 overweight, 30 and over obesity). BMI is a rough screening measure that does not account for muscle mass, age or body composition, and it is not a diagnosis.
Worked example
A person who is 70 kg and 175 cm tall has a BMI of 70 ÷ (1.75 × 1.75) = 22.9, which falls in the 18.5 to 24.9 range commonly labelled healthy weight for adults.
Common problems and fixes
- Muscular people score high.
- BMI does not separate muscle from fat. It is a screening measure, not a diagnosis.
- Units mixed up.
- Use kilograms and metres (or pounds and inches with the matching formula). Entering centimetres as metres gives nonsense.
- Children and teenagers.
- Adult ranges do not apply to children. Use growth charts from a paediatrician.
Next steps
Frequently asked questions
What are the BMI categories?
Under 18.5 underweight, 18.5 to 24.9 normal, 25 to 29.9 overweight, and 30 or more obesity, for adults.
Is BMI accurate for athletes?
Not always, because it does not separate muscle from fat.
Is this medical advice?
No. Speak to a health professional about your health.
Are my files uploaded to a server?
No. Everything runs inside your browser on your own device, so your files and text are never sent anywhere.
Is it really free?
Yes. There is no sign-up, no watermark and no limit on how often you use it.
Does it work on my phone?
Yes. It works in any modern browser on phones, tablets and computers. Very large files may be slow on older phones.