What is Body Mass Index (BMI)?
The body mass index (BMI) is a number derived from a formula, used to compare and analyse the health effects of weight on people of all ages and heights. Use our instant online body mass index calculator to find your current BMI measurement and learn how to measure your waist circumference.
Your body mass index measurement combined with your Waist Circumference measurement can be used to determine obesity and the increased risk for various diseases.
A high waist circumference is often associated with an increased risk for type 2 diabetes, cardiovascular disease, dyslipidemia and hypertension when your BMI is calculated between 25 and 34.9.
Waist Circumference measurement is handy for people whose BMI indicates they maybe normal or overweight. EG. an athlete with an increased muscle mass may have a BMI greater than 25 - making them overweight on the BMI scale, however a Waist Circumference measurement would indicate that they are in fact not overweight.
Men with a waist circumference more than 102 cm (40 in) and women with a waist circumference more than 88 cm (35 in) are at increased risk of developing health problems.
To properly measure your Waist Circumference: Find your upper hip bone, the waist is usually measured at one inch above the naval, place a measuring tape around the abdomen, be sure the tape is horizontal, the tape measure should be firm but should not compress the skin. Changes in your waist circumference over time can indicate an increase or decrease in your abdominal fat, an increase in abdominal fat is associated with an greater risk of developing heart disease.
Physical activity and good nutrition are key factors in a healthy lifestyle. See our Old and New Food Pyramid for daily healthy eating.
See how many calories you burn during certain activities How to Count and Calculate Calories
Is your weight in proportion with your height? See our Height to Weight Ratio Chart.
NOTE: For children aged 1 to 20 use our Body Mass Index Calculator for Children to calculate a child's BMI.
What the BMI numbers mean:
Below 18.5 Underweight
18.5 - 24.9 Normal
25.0 - 29.9 Overweight
30.0 and Above Obese.
BMI is only one piece of a person's health profile and just one of the many factors related to developing a serious disease.
There are other factors that are important when assessing your risk for chronic disease including:
- Your Blood Sugar Level
- Your Cholesterol Level
- Your Family History of diseases
- Your Daily Diet
- Your Waist Circumference
- Your Blood Pressure
- Amount of Physical Activity
The English and Metric formula for calculating BMI
The Imperial BMI Formula
Body Mass Index is calculated using pounds and inches with this equation:
BMI = (Weight in Pounds
(Height in inches) x (Height in inches) ) x 703
For example, a person who weighs 220 pounds and is 6 feet 3 inches tall has a BMI of 27.5
(75 inches) x (75 inches) ) x 703 = 27.5
The Metric BMI Formula
BMI = Weight in Kilograms
(Height in Meters) x (Height in Meters)
BMI = (Weight in Kilograms
(Height in centimeters) x (Height in centimeters) ) x 10,000 For example, a person who weighs 99.79 Kilograms and is 1.905 Meters (190.50 centimeters) tall has a BMI of 27.5. 99.79 Kg
(1.905 m) x (1.905 m) = 27.5