BMI Calculator — Body Mass Index Calculator
Last reviewed: April 2026
The Body Mass Index (BMI) calculator estimates a screening number derived from your height and weight. Developed in the 1830s by mathematician Adolphe Quetelet, BMI uses the formula weight (kg) ÷ height (m)² to place adults into one of four categories: underweight, normal weight, overweight, or obese. It is widely used by healthcare providers as an initial screening tool because it's quick and requires no equipment. However, BMI has well-documented limitations — it does not distinguish between muscle mass and fat, it does not account for age, ethnicity, or bone density, and a person with high muscle mass may be classified as "overweight" despite being very fit. Use this calculator for general reference only, and discuss your results with a healthcare provider for context.
Calculate Your BMI
What this means
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| Category | BMI Range | Description |
|---|---|---|
| Underweight | Below 18.5 | May indicate nutritional deficiency or other health issues |
| Normal Weight | 18.5 – 24.9 | Associated with lowest risk for weight-related conditions |
| Overweight | 25.0 – 29.9 | Elevated risk for cardiovascular disease and diabetes |
| Obese | 30.0 and above | Higher risk for serious health conditions; consult your doctor |
Your BMI on the Full Spectrum
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Imperial equivalent: BMI = (weight in lbs × 703) ÷ height in inches²
Source: World Health Organization, National Institutes of Health
Known Limitations of BMI
BMI is a population-level screening tool, not a direct measure of body fat or health. It does not account for:
Muscle mass: Athletes with high muscle mass often register as "overweight" or even "obese" by BMI despite having very low body fat. Age & sex: Older adults tend to carry more fat at the same BMI. Women generally have more fat than men at the same BMI. Ethnicity: Studies show that people of Asian descent face higher health risks at lower BMI thresholds. Fat distribution: Where fat is stored (abdomen vs. hips) matters significantly for health risk — BMI doesn't capture this. For a more complete picture, consider waist circumference, waist-to-hip ratio, or body fat percentage measurements.
Sources & Methodology
Formula: BMI = weight (kg) ÷ height (m)². Imperial: BMI = (weight in lbs × 703) ÷ height in inches².
Categories: Underweight <18.5 · Normal Weight 18.5–24.9 · Overweight 25.0–29.9 · Obese ≥30.0.
Sources: World Health Organization (WHO) BMI classification; National Institutes of Health (NIH) Clinical Guidelines on Obesity (1998). BMI is a population-level screening tool and does not directly measure body fat or health status.
Last reviewed: April 2026