How BMI is calculated
Body mass index is a ratio of weight to height. In metric units, BMI equals weight in kilograms divided by height in metres squared. In imperial units, BMI equals 703 multiplied by weight in pounds divided by height in inches squared. The result is matched to a standard adult category: underweight, normal weight, overweight, or obese.
Frequently asked questions
How is BMI calculated?
In metric units, BMI equals weight in kilograms divided by the square of height in metres. In imperial units, BMI equals 703 times weight in pounds divided by the square of height in inches.
What are the BMI categories?
Below 18.5 is underweight, 18.5 to 24.9 is normal weight, 25 to 29.9 is overweight, and 30 or above is obese.
Is BMI an accurate measure of health?
BMI is a simple screening tool, not a diagnosis. It does not distinguish muscle from fat and does not account for age, sex, or body composition.
Does this BMI calculator store my data?
No. All calculations run entirely in your browser. Nothing you enter is uploaded or saved on a server.
Can children use this BMI calculator?
This tool uses adult BMI ranges. BMI for children and teens is interpreted with age and sex percentile charts, so consult a healthcare provider.
Best picks: which tool fits your goal?
A quick comparison to point you to the right next tool.
| Goal | Tool | Best for |
|---|---|---|
| Hit daily protein, carb, and fat targets | Macro Calculator | Diet planning |
| Estimate daily calorie needs | Calorie Calculator | Weight goals |
| Estimate body fat percentage | Body Fat Calculator | More detail than BMI alone |
| Find a healthy weight for your height | Ideal Weight Calculator | Devine formula estimate |
Related calculators
Disclaimer: This BMI calculator is a screening tool for general informational purposes only and is not a diagnosis or medical advice. BMI does not measure body fat directly and may not apply to athletes, pregnant people, children, or older adults. Consult a qualified healthcare provider for any health concerns.