BMI Calculator
Calculate your Body Mass Index (BMI). Enter your height and weight to see your BMI and its standard category. This is a general screening estimate, not medical advice.
Example: with Height 5 ft · Weight 170 lb → Your BMI: 24.4.
- BMI Prime0.98
- Ponderal Index13.7 kg/m³
- Healthy weight for your height128.9 – 174.2 lb
Computed by the calculator below using its default values. Change any input to see your own numbers.
Where you land
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Check it outWhat BMI does and doesn't tell you
BMI is a quick screening number that relates weight to height. The standard categories are: under 18.5 underweight, 18.5–24.9 normal, 25–29.9 overweight, and 30+ obese. It doesn't distinguish muscle from fat, so very muscular people can read high. Treat it as a rough indicator and talk to a healthcare professional about your individual health.
| Classification | BMI range |
|---|---|
| Severe Thinness | Below 16 |
| Moderate Thinness | 16 – 17 |
| Mild Thinness | 17 – 18.5 |
| Normal | 18.5 – 25 |
| Overweight | 25 – 30 |
| Obese Class I | 30 – 35 |
| Obese Class II | 35 – 40 |
| Obese Class III | Above 40 |
How it’s calculated
BMI = 703 × weight (lb) ÷ height (in)². Categories: under 18.5 underweight, 18.5–24.9 normal, 25–29.9 overweight, 30+ obese.
BMI Prime is your BMI divided by the upper healthy-range boundary (25), so 1.0 marks that threshold. Ponderal Index is mass ÷ height cubed (kg/m³), a build measure that scales better than BMI for very short or very tall people. The healthy-weight range applies the 18.5–25 BMI band to your entered height.
Results update as you type and are estimates, not professional advice — verify important decisions with a qualified professional.
Sources: CDC / WHO BMI categories.
Common mistakes
- Treating BMI as body fat — it ignores muscle.
- Using it as a diagnosis rather than a screening number.
Frequently asked questions
Is BMI accurate for everyone?
No — it can overstate body fat for muscular people and understate it for others. It's a population screening tool, not a diagnosis.
What's a healthy BMI?
The 'normal' range is generally 18.5–24.9, but healthy weight varies by person. Discuss your situation with a professional.
How do I convert to metric?
BMI = weight (kg) ÷ height (m) squared. This tool uses the imperial formula (703 × lbs ÷ in²).