BMI is a way of measuring a person’s weight relative to his or her height. BMI expresses how thick or thin a person is in simple numeric terms, and allows doctors and other health professionals to discuss weight objectively on a standardized scale.
This BMI calculator converts units to satisfy the following BMI formula calculations.
- Metric units: BMI = weight (kg) ÷ height2 (m)
- US units: BMI = (weight (lb) ÷ height2 (in)) * 703
Normal Weight Range
Normal weight BMI is 18.5 to 24.9. To calculate your normal weight range use the following:
- Metric units:
minimum weight (kg) = 18.5 × height2 (m)
maximum weight (kg) = 24.9 × height2 (m)
- US units:
minimum weight (lb) = (18.5 ÷ 703) × height2 (in)
maximum weight (lb) = (24.9 ÷ 703) × height2 (in)
Example 1 (Calculating BMI in metric units)
Matilda weighs 64 kg and is 1.9 meters tall. What is her BMI?
- BMI = w ÷ h2
- BMI = 64 ÷ 1.92
- BMI = 64 ÷ 3.61
- BMI = 17.7
Example 2 (Calculating BMI in US units)
Stanley weighs 184 lb and is 5 feet, 10 inches tall. What is his BMI?
- 5 feet, 10 inches = 70 inches
- BMI = (w ÷ h2) * 703
- BMI = (184 ÷ 702) * 703
- BMI = (184 ÷ 4900) * 703
- BMI = 0.3755 * 703
- BMI = 26.4
Although BMI is calculated the same way worldwide for all ages, the way an individual’s BMI is interpreted depending on location and the person’s age:
- In many Southeast Asian countries, the thresholds for the overweight and obese categories tend to be lower. For example, in Singapore and Hong Kong a BMI of 23.0 is considered overweight, whereas in the United States a BMI of 25 is considered overweight.
- Children and adolescents are not evaluated using these thresholds at all, but are evaluated relative to others of the same age and gender:
Keep in mind that BMI is a ratio between height and total body weight – it does not differentiate between weight from muscle and weight from fat, nor does it consider an individual’s body frame type. BMI is one of several tools used to assess a person’s weight and overall health. If you are concerned about your weight, it is best to consult with your doctor or healthcare professional.
- “Body Mass Index,” Wikipedia, The Free Encyclopedia.
- “Healthy Weight,” Centers for Disease Control and Prevention.