BMI Calculator
Calculate your Body Mass Index instantly. Find out which category you fall in and see your healthy weight range.
Your BMI
What Is BMI?
Body Mass Index (BMI) is a widely used screening tool that estimates whether your weight is appropriate for your height. It's calculated as weight divided by height squared. While BMI doesn't directly measure body fat, it correlates strongly with body fat levels for most people and is used by healthcare providers worldwide.
BMI Categories
- Underweight: BMI below 18.5 — may indicate nutritional deficiency or health issues
- Normal weight: BMI 18.5–24.9 — associated with the lowest health risks
- Overweight: BMI 25–29.9 — increased risk for cardiovascular disease and diabetes
- Obese (Class I): BMI 30–34.9 — high health risk
- Obese (Class II): BMI 35–39.9 — very high health risk
- Obese (Class III): BMI 40+ — extremely high health risk
The BMI Formula
Metric: BMI = weight (kg) ÷ height (m)²
Imperial: BMI = 703 × weight (lb) ÷ height (in)²
Limitations of BMI
BMI is a useful screening tool but has important limitations:
- It doesn't distinguish between muscle and fat — very muscular individuals may have a "high" BMI despite being healthy
- It doesn't account for fat distribution (belly fat is more dangerous than hip/thigh fat)
- It may not be accurate for older adults (who naturally lose muscle mass) or very tall/short individuals
- It doesn't measure body composition — consider a body fat calculator for a more complete picture
Despite these limitations, BMI remains a quick and useful starting point for assessing healthy weight. For a more complete assessment, combine it with waist circumference and body fat percentage.
· Reviewed by the Vital Health Editorial Team
How This Calculator Works
This calculator computes Body Mass Index using the standard CDC and WHO formula: BMI = weight (kg) / height² (m²). For imperial units, the formula is BMI = 703 × weight (lb) / height² (in²). BMI categories follow WHO guidelines: underweight (<18.5), normal weight (18.5–24.9), overweight (25.0–29.9), and obese (≥30.0, with sub-classes I 30–34.9, II 35–39.9, III ≥40). BMI is a screening tool, not a diagnostic of body fatness or health.
This calculator is for informational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
Frequently Asked Questions
Is BMI accurate for athletes or muscular people?
No. BMI does not distinguish between muscle and fat. A bodybuilder with 10% body fat may register as 'obese' on the BMI scale because muscle is denser than fat. For athletes, body fat percentage (measured via DEXA, calipers, or the Navy method) is a more accurate health indicator than BMI.
What BMI is considered healthy?
According to the WHO, a BMI of 18.5–24.9 is considered normal weight. Research consistently shows the lowest mortality risk in this range. A BMI of 25.0–29.9 (overweight) is associated with moderately increased health risks, while BMI ≥30 (obese) significantly increases risk for heart disease, type 2 diabetes, and certain cancers.
Does BMI account for age or gender?
Standard BMI does not adjust for age or sex, even though body fat distribution changes with both. Older adults naturally carry more body fat at the same BMI, and women tend to have more body fat than men at the same BMI. Some researchers advocate for age-adjusted BMI standards.
Sources & References
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