Loading SnapFreeTools...
Loading SnapFreeTools...
Calculate your Body Mass Index in metric (kg/cm) or imperial (lb/ft). See your BMI category, healthy weight range, and how to interpret your result.
Enter your height and weight to calculate your BMI.
BMI is a screening measure and does not directly measure body fat or diagnose any health condition. Muscle mass, age, sex, and body composition can all affect how BMI should be interpreted. This calculator is for informational purposes only. For personal medical advice, please consult a qualified healthcare professional.
Body Mass Index (BMI) is a simple numerical value derived from a person's weight and height. It is widely used as a population-level screening measure to classify adults into weight categories. The standard adult BMI categories are defined by the World Health Organization (WHO) and adopted by health agencies worldwide.
BMI does not directly measure body fat. Two people can have identical BMI values but very different body compositions — for example, an athlete with high muscle mass and a sedentary person with high body fat. For this reason, BMI is best used as one data point in a broader health assessment.
Example: 70 kg ÷ (1.75 × 1.75) = 22.9
Example: 703 × 154 ÷ (69 × 69) = 22.7
| BMI Range | Category | Classification |
|---|---|---|
| Below 18.5 | Underweight | WHO Standard |
| 18.5 – 24.9 | Healthy Weight | WHO Standard |
| 25.0 – 29.9 | Overweight | WHO Standard |
| 30.0 – 34.9 | Obesity Class I | WHO Standard |
| 35.0 – 39.9 | Obesity Class II | WHO Standard |
| 40.0 and above | Obesity Class III | WHO Standard |
BMI is a useful population-level screening tool, but it has several important limitations:
BMI, or Body Mass Index, is a numerical value calculated from a person's weight and height. It provides a simple screening measure used to classify adults into weight categories such as underweight, healthy weight, overweight, and various classes of obesity. The formula is: BMI = weight(kg) ÷ height(m)².
For metric units: BMI = weight in kilograms ÷ (height in meters)². For imperial units: BMI = 703 × weight in pounds ÷ (height in inches)². For example, a person who weighs 70 kg and is 1.75 m tall has a BMI of 70 ÷ (1.75 × 1.75) = 22.9.
For adults, a BMI between 18.5 and 24.9 is generally considered the standard healthy weight range according to the WHO and CDC. Below 18.5 is classified as underweight, and 25.0 or above is classified as overweight.
A BMI of exactly 18.5 falls at the lower boundary of the standard healthy weight range. Any BMI below 18.5 is classified as underweight, which may indicate insufficient body weight for optimal health.
A BMI of 25.0 falls at the boundary between healthy weight and overweight. A value of 25.0 or above but below 30.0 is classified as overweight according to standard adult BMI categories.
A BMI of 30.0 or above is classified as Obesity Class I. At this threshold, standard health guidelines typically recommend consulting a healthcare professional about weight management strategies.
First convert your height from centimeters to meters by dividing by 100 (e.g., 175 cm = 1.75 m). Then use the formula: BMI = weight(kg) ÷ height(m)². Example: 72 kg ÷ (1.75 × 1.75) = 72 ÷ 3.0625 = 23.5.
Use the imperial formula: BMI = 703 × weight(lb) ÷ height(in)². First convert your height entirely into inches (e.g., 5 feet 9 inches = 69 inches). Example: 703 × 160 ÷ (69 × 69) = 703 × 160 ÷ 4761 = 23.6.
BMI is a useful population-level screening tool but has well-known limitations. It does not directly measure body fat, muscle mass, or body composition. A highly muscular person may have a high BMI without excess body fat, while an older person may have a normal BMI despite having little muscle mass. BMI should be interpreted alongside other health assessments.
No. BMI does not distinguish between muscle and fat. An athlete with high muscle mass may be classified as overweight or obese by BMI despite having low body fat. This is a key limitation of BMI as a health screening measure.
The BMI formula itself does not change with age for adults, but interpretation may vary. Some research suggests that older adults may carry slightly more body fat at the same BMI than younger adults. For children and adolescents, entirely different age- and sex-specific BMI-for-age charts must be used rather than the adult BMI categories.
The standard adult BMI formula is the same for both men and women. However, at the same BMI, women tend to have higher body fat percentages than men. For this reason, some health researchers suggest gender-specific interpretations, but the standard BMI categories published by the WHO and CDC apply equally to both sexes.
No. The adult BMI calculator and its standard weight categories (underweight, healthy, overweight, obese) should not be applied to children and adolescents under 18. For people under 18, BMI-for-age percentile charts based on age and sex are required. Consult a pediatrician for proper assessment.
For adults, a healthy weight corresponds to a BMI between 18.5 and 24.9. For someone who is 1.75 m (5'9") tall, the formula gives: minimum = 18.5 × (1.75)² = 56.6 kg; maximum = 24.9 × (1.75)² = 76.2 kg. Our calculator shows this range automatically after you enter your height.
Standard adult BMI categories: Underweight (below 18.5), Healthy Weight (18.5–24.9), Overweight (25.0–29.9), Obesity Class I (30.0–34.9), Obesity Class II (35.0–39.9), Obesity Class III (40.0 and above). These categories are defined by the WHO and are used in most clinical and public health contexts.
There is no strict rule, but many health guidelines suggest checking BMI once per year as part of a routine health review. More frequent tracking can be helpful when actively managing weight, but BMI alone is not a day-to-day health monitoring tool.
A BMI of 25.0–29.9 is classified as overweight. A BMI of 30.0 or above is classified as obese. Within obesity, there are three classes: Class I (30–34.9), Class II (35–39.9), and Class III (40+). These distinctions are used to assess relative health risk and guide clinical decision-making.