About BMI Calculator
This BMI calculator works out body mass index from your weight and height. Choose metric (kilograms and centimetres) or imperial (pounds, feet and inches), and the tool shows your BMI to one decimal place, the category, and the weight range that corresponds to a BMI of 18.5 to 24.9 at your height. The categories used are underweight, healthy weight, overweight and obese.
BMI is a simple screening number based on weight divided by height squared. It does not measure body fat, muscle, age or health, so treat the result as an estimate for information only, not a diagnosis or medical advice. For decisions about your health, speak to a doctor or qualified health professional. Your numbers stay in your browser.
How to use BMI Calculator
- 01
Choose metric or imperial.
- 02
Enter your weight and height.
- 03
See your BMI and healthy weight range.
When to use it
- Get a quick reference number before a routine conversation with a doctor.
- Find the weight range that matches a BMI of 18.5 to 24.9 for your height.
- Check BMI using pounds, feet and inches without converting units by hand.
- Compare your BMI before and after a change in weight.
- Understand what the underweight, healthy, overweight and obese categories mean in numbers.
Frequently asked questions
How is BMI calculated?
BMI equals weight in kilograms divided by height in metres squared. For 70 kg and 175 cm, that is 70 / (1.75 x 1.75), about 22.9. In imperial units the tool first converts pounds and inches to metric.
What BMI categories does the calculator use?
Below 18.5 is underweight, 18.5 to 24.9 is healthy weight, 25 to 29.9 is overweight, and 30 or above is obese. These are general adult ranges and are not a medical diagnosis.
Is BMI accurate for everyone?
No. BMI does not separate muscle from fat and ignores age, sex and body shape, so athletes and older adults may get misleading results. It is a rough screening tool. Ask a health professional for a proper assessment.
Can I use pounds, feet and inches?
Yes. Switch Units to Imperial, then enter weight in pounds and height in feet and inches. The tool converts to metric internally and shows the healthy weight range in both kilograms and pounds.
Is this calculator suitable for children?
No. The categories shown are meant for adults. Children and teenagers are assessed using age and sex based growth charts, so ask a paediatrician or other health professional for advice.
Is my weight and height data stored?
No. The calculation runs in your browser and nothing is uploaded or saved. Results are estimates for information only and are not a substitute for professional medical advice.