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Calculator Use

The BMI calculation for women is the same as the calculation for men. For adults over the age of 20 the BMI is calculated by dividing weight by height squared. The BMI formula you use depends on your units of measure.

The BMI Calculation

If you're using meters and kg the BMI formula is:

If your BMI measurements are in cm and kg use the BMI formula above and multiply the result by 10,000.

If you're using feet, inches and pounds the BMI formula is the same except you need to convert feet to inches and multiply the result by 703 as below:

How to Find BMI

After you calculate your BMI number use a BMI chart to find your weight category. The CDC BMI chart uses 4 weight categories to classify adults as underweight, normal weight, overweight and obese. The WHO BMI chart is more descriptive particularly where BMI is over 25.

It's important to keep in mind that while the BMI computation is the same for men and women these generic BMI charts do not account for physical characteristics that differ between men and women. Men tend to have more muscle weight than women, for example. BMI charts also may not accurately represent bodyweight health in people of short stature or in athletes who have a lot of muscle.

Examples of How to Calculate BMI Using the Formulas

Using metric units, where weight is in kilograms and height is in meters, divide weight by meters squared. The metric BMI formula is:

BMI = weight (kg) ÷ height² (meters)

Using US units, where weight is in pounds and height is in inches, divide weight by inches squared. Then multiply this number by 703. The US BMI formula is:

BMI = weight (lb) ÷ height² (inches) * 703

Example BMI Calculation in Metric Units

Matilda weighs 64 kg and is 1.9 meters tall. What is her BMI?

Divide 64 kg by 1.9² m

• BMI = w ÷ h²
• BMI = 64 ÷ 1.9²
• BMI = 64 ÷ 3.61
• BMI = 17.7

Referencing the charts above you can see that a BMI of 17.7 puts Matilda in the underweight BMI category.

Example BMI Calculation in US Units

Stella weighs 184 lb and is 5 feet, 10 inches tall. What is her BMI?

Find total inches by multiplying 5 * 12 and add 10. Then divide weight by total inches squared, and multiply the result by 703.

• 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

Referencing the charts above you can see that a BMI of 26.4 puts Stella in the overweight BMI category.

What is the BMI Test?

The body mass index or BMI is a ratio of mass to height. It is calculated as kg per square meter or pounds per square inch of height.

Although BMI is calculated the same way for all ages internationally, the way BMI is interpreted depends on country 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 but are evaluated relative to other children 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 type of body frame. 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.

For additional information about the BMI calculation see our Adult BMI Calculator.

BMI and Normal Weight Range

Normal weight BMI is 18.5 to 24.9. To calculate your normal weight range use the following formulas:

• Calculate normal weight range in metric units:
  minimum weight (kg) = 18.5 × height² (m)
  maximum weight (kg) = 24.9 × height² (m)
• Calculate normal weight range in US units:
  minimum weight (lb) = (18.5 ÷ 703) × height² (in)
  maximum weight (lb) = (24.9 ÷ 703) × height² (in)

References

• "Body Mass Index," Wikipedia, The Free Encyclopedia.
• "Healthy Weight," Centers for Disease Control and Prevention.