An online BMI calculator metric and BMI imperial calculator tool to calculate body mass index for adult. BMI - Body mass index is a measure of body fat based on height and weight that applies to adult men and women. Although BMI is often considered an indicator of body fatness, it is a surrogate measure of body fat because it measures excess weight rather than excess fat.

Very Severely Underweight | Less than 15 |

Severely Underweight | Between 15 - 16 |

Underweight | Between 16 - 18.5 |

Normal Weight | Between 18.5 - 24.9 |

Overweight | Between 25 - 29.9 |

Moderately Obese | Between 30 - 35 |

Severely Obese | Between 35 - 40 |

Very Severely Obese | 40 or greater |

BMI = mass (kg) / height^{2} (m)

With the metric system, the formula for BMI is weight in kilograms divided by height in meters squared. Since height is commonly measured in centimeters, an alternate calculation formula, dividing the weight in kilograms by the height in centimeters squared, and then multiplying the result by 10,000, can be used.

When using English measurements or Imperial system, ounces (oz) and fractions must be changed to decimal values. Then, calculate BMI by dividing weight in pounds (lbs) by height in inches (in) squared and multiplying by a conversion factor of 703.

BMI = 703 × mass (lbs) / height^{2}(in)

For children, BMI differs by age and gender. BMI is used as a screening tool to identify possible weight problems for children. For children and teens, BMI is age- and gender-specific and is often referred to as BMI-for-age. BMI is calculated using the same method as adults, but is expressed, not as an absolute value, but as a percentile which can be obtained from either a graph or a percentile calculator. These percentiles express a child’s BMI relative to other children of the same gender and age.

Underweight: Less than the 5th percentile

Healthy weight: 5th percentile to less than the 85th percentile

Overweight 85th to less than the 95th percentile

Obese: Equal to or greater than the 95th percentile

The clinical limitations of BMI should be considered. BMI is a surrogate measure of body fatness because it is ameasure of excess weight rather than excess body fat. Factors suchas age, sex, ethnicity, and muscle mass can influence therelationship between BMI and body fat.