How accurate is the BMI chart?

One way to see if your weight is healthy is to calculate your body mass index (BMI), which considers your height and weight in determining whether you have a healthy or unhealthy percentage of body fat.
The BMI is a good, but imperfect guide. As muscles weigh more than fat, people who are very muscular and physically fit with a low percentage of body fat can have the same high BMI as an overweight person with a lot of body fat.
Because of this, waist circumference is a more useful tool to determining how much abdominal fat a person has. Using this method, men are considered overweight if their waist measurement is greater than 40 inches and women are overweight if their waist measurement is greater than 35 inches.
If you are an average person (not a bodybuilder) you can still use the BMI to determine if you are overweight.
The BMI is calculated by using the following formula: ((mass(lb.) / (height(in.))2) x 703
A BMI of 18.5 – 24.9 is considered normal, 25 – 29.9 is considered overweight and a BMI of 30 and above is considered obese. People with a BMI less than 18.5 are considered underweight.