A body fat calculator helps to keep your body mass in balance.

Using a body fat calculator to keep weight in line promotes better health.

A body fat calculator simply measures the ratio of lean body mass to fat body mass.  Too much fat can lead to health problems like heart disease, diabetes, high cholesterol and other serious conditions.  By using a body mass calculator to determine if you are keeping your body fat within a reasonable level, you'll be healthier and, of course, slimmer. For women, an acceptable percentage is between 25 - 31%.  For men, it's 18 - 25%.  Any number over that is considered obese. 

One form of body fat calculator uses calipers to measure skin fold thickness at several areas of your body. An expert pinches your skin at different areas and measures them with calipers. The results are plugged into a formula to determine your body fat. The result is based on the idea that thickness of fat under the skin reflects total body fat. This type of body fat calculator can be as accurate as other methods, but usually isn't.  It depends on the skill of the tester.

Another body fat calculator uses bioelectrical impedance analysis (BIA) to perform measurements. Either using a handheld scale or standing on a BIA scale, a signal passes either from hand to hand or foot to foot. The faster the signal travels, the more muscle you have. The results are based on the fact that water conducts electricity.  Fat contains almost no water while muscle is about 70% water. This type of body fat calculator CAN be accurate (4% margin of error) but the results are affected by hydration, food intake and skin temperature.  If you're dehydrated, you're body fat percentage will read higher than it is.