BMI stands for Body Mass Index. It is a measure of body composition. BMI is calculated by taking a person's weight and dividing by their height squared. For instance, if your height is 1.82 meters, the divisor of the calculation will be (1.82 * 1.82) = 3.3124. If your weight is 70.5 kilograms, then your BMI is 21.3 (70.5 / 3.3124) (see calculator links below).

The higher the figure the more overweight you are. Like any of these types of measures it is only an indication and other issues such as body type and shape have a bearing as well. Remember, BMI is just a guide - it does not accurately apply to elderly populations, pregnant women or very muscular athletes such as weight lifters.

Test Details

• equipment required: scalesand stadiometer as for weight and height.
• procedure: BMI is calculated from body mass (M) and height (H). BMI = M / (H x H), where M = body mass in kilograms and H = height in meters. The higher the score usually indicating higher levels of body fat.
• scoring: Use the table below to determine your BMI rating. The table shows the World Health Organization BMI classification system. The rating scale is the same for males and females. You can also use the reverse lookup BMI table for determining your ideal weight based on height.

classification	BMI (kg/m2)	sub-classification		BMI (kg/m2)
underweight	< 18.50	Severe thinness		< 16.00
		Moderate thinness		16.00 - 16.99
		Mild thinness		17.00 - 18.49
normal range	18.5 - 24.99	normal		18.5 - 24.99
overweight	≥ 25.00	pre-obese		25.00 - 29.99
		Obese (≥ 30.00)	obese class I	30.00 - 34.99
			obese class II	35.00 - 39.99
			obese class II	≥ 40.00

source: World Health Organization

• target population: BMI is often used as a general population measure to determine the level of health risk associated with obesity.
• advantages: only simple calculations are required from standard height and weight measurements.
• disadvantages: in certain populations BMI can be inaccurate as a measure of body fatness, for example large and muscular though lean athletes may score high BMI levels which incorrectly rates them as obese.
• other comments: Other simple measures of body composition, such as skinfolds measures, would be preferable if available.