Body Mass Index (BMI) is a height-adjusted weight index for adults used to categorize weight status.

How do you calculate BMI?

BMI is calculated as weight(kg) divided by height(m)^2, or (lb / in^2) × 703. The calculator performs this automatically.

What are the BMI categories?

Common adult categories: Underweight <18.5; Normal 18.5–24.9; Overweight 25–29.9; Obesity ≥30.

Is BMI accurate for athletes?

BMI does not distinguish muscle from fat, so athletes may appear overweight. Use body fat percentage and waist measures for context.

Does age or sex change BMI cut-offs?

Standard adult BMI cut-offs are the same across age and sex, but interpretation should consider body composition and individual factors.

How often should I recheck BMI?

Recalculate after meaningful weight changes or every few weeks during active weight management.

BMI Calculator

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BMI Categories

Category	BMI
Underweight	< 18.5
Normal	18.5–24.9
Overweight	25–29.9
Obese	30+

About BMI Calculator

The Body Mass Index (BMI) Calculator estimates weight status for adults using the formula BMI = weight(kg) / height(m)². It’s a quick screening tool for population health and individual trend tracking. Because BMI does not distinguish muscle from fat, pair it with body fat % and waist measures for context.

How to use this BMI Calculator

Enter height and weight (metric or US units) and press Calculate.
Compare your BMI to standard adult ranges (underweight, normal, overweight, obesity).
Use complementary tools (Body Fat, WHtR) to refine risk and track change over time.

Notes & limits

BMI is for adults; growth charts should be used for children/teens.
Highly muscular or older adults may need additional measures beyond BMI.
Trends over weeks/months are more informative than a single reading.

FAQ

What is BMI?
A height-adjusted weight index for adults used to categorize weight status.
How do you calculate BMI?
Use kg/m² or (lb / in²) × 703. This calculator handles the math automatically.
What are the BMI categories?
Underweight <18.5, Normal 18.5–24.9, Overweight 25–29.9, Obesity ≥30.
Is BMI accurate for athletes?
Muscular people may score higher BMI without excess fat. Check body fat % and waist measures too.
Does age or sex change BMI cut-offs?
Standard adult cut-offs are the same; interpretation should still consider age, sex, and body composition.
How often should I recheck BMI?
Recalculate after meaningful weight changes or every few weeks during active weight management.

Disclaimer

The tools provided on this site are intended for educational and informational purposes only and are not a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of a qualified health provider with any questions you may have about a medical condition. If you think you may have a medical emergency, call your local emergency number immediately.

Formulas are estimates and may be less accurate for athletes, bodybuilders, older adults, and certain body types.