Body Mass Index (BMI) may be a person's weight in kilograms divided by the sq. of height in meters. A high BMI are often associate degree indicator of high body avoirdupois. BMI are often wont to screen for weight classes which will result in health issues however it's not diagnostic of the body avoirdupois or health of a private. Body mass index (BMI) is a value derived from the mass (weight) and height of a person. The BMI is defined as the body mass divided by the square of the body height, and is universally expressed in units of kg/m2, resulting from mass in kilograms and height in meters. The BMI may be determined using a table or chart which displays BMI as a function of mass and height using contour lines or colors for different BMI categories, and which may use other units of measurement (converted to metric units for the calculation). The BMI is a convenient rule of thumb used to broadly categorize a person as underweight, normal weight, overweight, or obese based on tissue mass (muscle, fat, and bone) and height. Commonly accepted BMI ranges are underweight (under 18.5 kg/m2), normal weight (18.5 to 25), overweight (25 to 30), and obese (over 30). BMIs under 20 and over 25 have been associated with higher all-causes mortality, with the risk increasing with distance from the 20–25 range.