BMI Calculator

BMI stands for Body Mass Index. It's a simple numerical measure that uses your height and weight to work out if your weight is healthy. The BMI is calculated as your weight (in kilograms) divided by the square of your height (in meters).

BMI was developed in the 19th century by Adolphe Quetelet, a Belgian mathematician and astronomer. It gained widespread use in the 20th century as a quick screening tool for weight categories—underweight, healthy weight, overweight, and obesity.

While BMI is a useful screening tool, it doesn't directly measure fat or distinguish between muscle and fat. However, it remains the most widely used method for assessing weight status at a population level due to its simplicity and low cost.

For adults (20 years and older), BMI categories follow World Health Organization (WHO) standards. These categories are used internationally and are associated with different health risks.

BMI Classification (WHO Standards)

For children and teenagers, BMI interpretation differs. Since fat levels change with age and vary between boys and girls, BMI is compared to CDC growth charts that show child percentiles for the same age group.

BMI Percentile Categories (CDC)

Percentiles tell you how a child's BMI compares to other children of the same age group. For example, at the 60th percentile means the child's BMI is higher than 60% of children and lower than 40% of children in that group.

Sources: CDC (Centers for Disease Control and Prevention)

Our BMI Calculator provides accurate results for both adults and children using internationally recognized standards.

For Adults (20+ years)

1. Select your preferred unit system (Metric or Imperial)
2. Select gender (Male or Female)
3. Enter age (20-120 years)
4. Enter your height (cm or ft/in)
5. Enter your weight (kg or lbs)
6. Click "Calculate BMI" to see your results
7. Review your BMI value, category, and healthy weight range

For Children/Teens (2-19 years)

1. Click the "Children/Teens" tab at the top
2. Select gender (Male or Female)
3. Enter age (2-19 years)
4. Enter height (cm or ft/in)
5. Enter weight (kg or lbs)
6. Click "Calculate BMI" to see results from CDC growth charts
7. Review the BMI value, percentile, and weight status category

Tip: For accurate results, take measurements without shoes and in light clothing.

While BMI serves as a useful screening tool, it has important limitations to consider:

Limitations in Adults

• Can't distinguish muscle from fat: Muscular people (e.g., athletes) may be classified as overweight/obese despite low fat; "skinny fat" individuals may appear normal.
• Ignores fat distribution: Doesn't detect dangerous abdominal/visceral fat linked to higher risks of heart disease and diabetes.
• Racial/ethnic differences: Standard cutoffs fit European populations best; Asians often have higher fat and risks at lower BMI (e.g., WHO suggests overweight at ≥23 kg/m² for Asians).
• Demographic factors: Older adults may have normal BMI but high fat due to muscle loss; women typically have more fat than men at the same BMI.
• Not ideal for everyone: Misleading in pregnant women, elderly with edema, or extreme builds; not a standalone diagnostic tool (AMA recommends combining with waist circumference, etc.).

Limitations in Children and Teens

(Uses age-specific percentiles)

• Can't distinguish fat from muscle: Growth spurts or athleticism can lead to misclassification.
• Affected by puberty and growth: Rapid changes reduce accuracy; doesn't account for puberty timing or ethnic differences in body composition.
• Limited precision: Weakly correlates with actual fat levels, especially in younger kids; may under- or over-estimate risks.
• Reference chart biases: Charts (e.g., CDC) may not fit all ethnic groups; can cause unnecessary stigma.

Recommendation: Use BMI as a starting point for health assessment. For a complete picture, consider other measures such as waist circumference, body fat percentage, and consultation with a healthcare provider.