BMI Calculator is a measure of body fat based on height and weight that applies to adult men and women.
Body mass index (BMI) is a person’s weight in kilograms divided by the square of height in meters. BMI is an inexpensive and easy screening method for weight category—underweight, healthy weight, overweight, and obesity.
BMI does not measure body fat directly, but BMI is moderately correlated with more direct measures of body fat. Furthermore, BMI appears to be as strongly correlated with various metabolic and disease outcome as are these more direct measures of body fatness.
BMI is calculated the same way for both adults and children. The calculation is based on the following formulas:
| Measurement Units | Formula and Calculation |
|---|---|
| Kilograms and meters (or centimeters) |
Formula: weight (kg) / [height (m)]2 With the metric system, the formula for BMI is weight in kilograms divided by height in meters squared. Because height is commonly measured in centimeters, divide height in centimeters by 100 to obtain height in meters. Example: Weight = 68 kg, Height = 165 cm (1.65 m) |
| Pounds and inches |
Formula: weight (lb) / [height (in)]2 x 703 Calculate BMI by dividing weight in pounds (lbs) by height in inches (in) squared and multiplying by a conversion factor of 703. Example: Weight = 150 lbs, Height = 5’5″ (65″) |
This is the World Health Organization's (WHO) recommended body weight based on BMI values for adults. It is used for adults 20 years old and older, BMI is interpreted using standard weight status categories. These categories are the same for men and women of all body types and ages.
The standard weight status categories associated with BMI ranges for adults are shown in the following table.
| Category | BMI range - kg/m2 |
|---|---|
| Very severely underweight | < 15 |
| Severely underweight | 15 - 16 |
| Underweight | 16 - 18.5 |
| Normal (healthy weight) | 18.5 - 25 |
| Overweight | 25 - 30 |
| Obese Class I (Moderately obese) | 30 - 35 |
| Obese Class II (Severely obese) | 35 - 40 |
| Obese Class III (Morbid) | < 40 |
For example, here are the weight ranges, the corresponding BMI ranges, and the weight status categories for a person who is 5′ 9″.
| Height | Weight Range | BMI | Weight Status |
|---|---|---|---|
| 5′ 9″ | 124 lbs or less | Below 18.5 | Underweight |
| 125 lbs to 168 lbs | 18.5 to 24.9 | Normal or Healthy Weight | |
| 169 lbs to 202 lbs | 25.0 to 29.9 | Overweight | |
| 203 lbs or more | 30 or higher | Obese |
The body mass index for children is calculated the same way as for adults, however it is then compared to values recorded for children of the same age group. As opposed to using pre-established thresholds for underweight and overweight, a BMI percentile is used to compare children of the same gender and age.
This is the "Centre for Disease Control and Prevention (CDC)" recommendation in terms of BMI categorization for children and teens with ages raging between age 2 and 20.
| Category | Percentile (%) Range |
|---|---|
| Underweight | < 5% |
| Healthy weight | 5% - 85% |
| At risk of overweight | 85% - 95% |
| Overweight | < 95% |