BMI Calculator

For most adults aged 20 and older, a BMI between 18.5 and 24.9 is considered healthy regardless of age. A BMI below 18.5 indicates underweight, 25–29.9 is overweight, and 30 or above is classified as obese. However, for adults over 65, some research suggests a slightly higher BMI (up to 27) may be protective, so it is always best to discuss your individual result with a healthcare provider.

At 5'4" (163 cm) and 140 lbs (63.5 kg), your BMI is approximately 24.0, which falls within the healthy weight range of 18.5–24.9. This means 140 lbs is not considered overweight for that height. BMI is a useful screening tool, but body composition factors like muscle mass and bone density also matter for a complete health picture.

For seniors (adults 65 and older), a BMI between 22 and 27 is generally considered healthy, and some guidelines allow a slightly wider range than for younger adults. Maintaining adequate muscle mass becomes more important with age, so weight alone is less telling than overall fitness and strength. A doctor or dietitian can help seniors set an appropriate weight goal based on their individual health status.

BMI is calculated by dividing your weight in kilograms by the square of your height in meters: BMI = kg / m². In imperial units, the formula is BMI = (lbs / inches²) × 703. For example, a person who is 5'9" (175 cm) and weighs 160 lbs (72.5 kg) has a BMI of roughly 23.6, which is in the healthy range. Our free calculator above handles both metric and imperial units automatically.

The World Health Organization (WHO) and CDC define four standard BMI categories for adults: Underweight (BMI below 18.5), Normal weight (18.5–24.9), Overweight (25.0–29.9), and Obese (30.0 and above). Obesity is further divided into Class I (30–34.9), Class II (35–39.9), and Class III, also called severe obesity (40 and above). These ranges apply to adults 20 years and older; children and teens use age- and sex-specific BMI percentile charts instead.

BMI uses the same formula and thresholds for both men and women, but research shows it can slightly underestimate body fat in women and overestimate it in muscular men. Women naturally carry more body fat than men at the same BMI, so some clinicians use waist circumference or body-fat percentage as complementary measures. Despite its limitations, BMI remains a widely used, free, and non-invasive screening tool recommended by the CDC and WHO.

Standard adult BMI calculators are not appropriate for children and teens aged 2–19 because healthy body fatness changes significantly as children grow. For this age group, the CDC recommends using a BMI-for-age percentile chart, where a result at or above the 95th percentile is considered obese and below the 5th percentile is underweight. Pediatric BMI must always be interpreted by a healthcare professional alongside growth chart trends.