Remember that a percent is a ratio, which means that the numerator and denominator must have the same units. Fractions in which the numerator and denominator have different units are called rates, as in "dollars per hour" or "miles per gallon."

Did you know that a body fat index calculator needs more information than your weight and height to produce accurate results. Some will ask for your waist, neck, and wrist sizes.

You can use Active.com's body fat index calculator or use a search engine to search for the phrase "body fat index calculator." Calculate your body fat percentage using several different calculators and compare the results.

In each case, divide the number of pounds by the total weight (in pounds). When doing this with a spreadsheet, you can specify how many digits you want displayed in the result.