BMI charts are tools used to assess a person's body mass index, or BMI, which is a measure of body fat based on height and weight. These charts categorize individuals into different weight status groups, such as underweight, normal weight, overweight, and obese. By comparing a person's BMI value to the ranges provided in the chart, one can quickly determine their weight category. To calculate BMI, you divide a person's weight in kilograms by their height in meters squared. For example, a person weighing 70 kg and standing 1.75 meters tall would have a BMI of 22.9, which falls within the normal weight range. BMI charts are widely used in healthcare to help identify potential health risks associated with being underweight or overweight.