BMI Calculator
Quick answer: BMI (body mass index) is weight in kilograms divided by height in metres squared. A person who weighs 70 kg and is 175 cm tall has a BMI of 22.9, which is in the normal range. It is a screening number, not a diagnosis.
Use the BMI Calculator
BMI formula and what each symbol means
BMI = weight (kg) ÷ height (m)². In pounds and inches: BMI = 703 × weight (lb) ÷ height (in)².
| Symbol | Meaning |
|---|---|
| weight | Body weight in kg or lb |
| height | Height in metres or inches |
BMI examples
Metric
70 kg and 175 cm (1.75 m). BMI = 70 ÷ (1.75 × 1.75) = 70 ÷ 3.0625 = 22.9.
Imperial
160 lb and 5 ft 8 in (68 in). BMI = 703 × 160 ÷ 68² = 112,480 ÷ 4,624 = 24.3.
How to calculate BMI step by step
- Measure height without shoes and weight in light clothing.
- Convert height to metres (cm ÷ 100).
- Square the height.
- Divide weight by that number.
How to read your BMI result
WHO adult ranges: under 18.5 underweight; 18.5 to 24.9 normal; 25 to 29.9 overweight; 30 and above obese. Indian consensus guidelines (2009) use lower cut-offs for Asian Indians: 23 to 24.9 overweight and 25 and above obese, because health risk rises at lower BMI in South Asian adults.
Common mistakes when calculating BMI
- Using this for children, who need age-and-sex percentile charts.
- Treating BMI as a diagnosis; it ignores muscle, bone and fat distribution.
- Mixing units, such as pounds with centimetres.
BMI FAQ
What is a healthy BMI?
For most adults, 18.5 to 24.9 is the normal range by WHO. Indian consensus guidelines treat 23 and above as overweight, so a healthier range for Asian Indians is about 18.5 to 22.9.
Is BMI accurate for athletes?
Not always. Muscle weighs more than fat, so a muscular person can have a high BMI without excess body fat.
Is BMI the same for men and women?
The formula and adult ranges are the same, but body fat differs between sexes, so waist size and other checks add useful context.
When should I see a doctor about my BMI?
If your BMI is under 18.5 or over 30, or you have unplanned weight change, speak to a doctor. They can check waist size, blood tests and other risks.
Method, review and disclaimer
Edited by: Hemant Kumar and Anjita Rai, founders of ToolsVault (SEO and content professional, not a licensed adviser). Method: this tool runs in your browser using the formula shown on this page; the numbers you enter are not sent to our servers. Sources: WHO: Obesity and overweight, Misra et al. 2009, Consensus statement for diagnosis of obesity in Asian Indians (J Assoc Physicians India)
Disclaimer: Not medical advice. Talk to a qualified clinician about your health.