How to Find Your Body Fat Index

Men and women are built differently, so their body fat indices are calculated differently.

The body fat index is a standard developed by the American Council on Exercise that places individuals into categories -- essential fat, athletes, fitness, acceptable and obese -- based on their body fat percentages. Different calculations are necessary to determine body fat percentages in men and women. For men 20 to 40 years old, body fat between 8 and 19 percent is considered healthy, while the range is 21 to 33 percent for women of the same age.

Things You'll Need

• Scale
• Tape measure

Instructions

Men

1. Weigh yourself and insert your body weight in pounds into the following formula: Weight x 1.082 + 94.42.

2. Measure your waist in inches and multiply the result by 4.15.

3. Subtract the answer to Step 2 from the answer to Step 1.

4. Subtract the result of Step 3 from your total body weight, which is the number you got after weighing yourself in Step 1.

5. Multiply the result from Step 4 by 100 and then divide by your total body weight. Compare your results to the chart in the Resource section, which displays fat percentages for men and women across categories.

Women

1. Weigh yourself and insert your body weight in pounds into the following formula: Weight x 0.732 + 8.987.

2. Measure your wrist at its thickest point and divide the result by 3.14. Measure your waist at the naval and multiply the result by .157. Measure your hip at its thickest point and multiply the result by .249. Measure your forearm at its thickest point and multiply by .434.

3. Add up your result from Step 1 and all of your results from Step 2 -- five numbers total -- to determine your lean body mass.

4. Subtract your lean body mass from your total body weight, which is the number you got after weighing yourself in Step 1.

5. Multiply the result from Step 4 by 100 and then divide by your total body weight. Compare your results to the chart at the Diet & Fitness Today website, which displays fat percentages for men and women across categories.

Tips & Warnings

• Measurements of your waist and body weight are the most accurate early in the morning after a full night of sleep.

• These formulas give you a good idea of where you stand -- the most accurate method of calculating body fat is a suspended underwater scale system only found at some universities and research laboratories.

References

• BuiltLean.com: Ideal Body Fat Percentage Chart: How Lean Should You Be?
• BMI Calculator: Body Fat Formula

Resources

• Diet & Fitness Today: Body Fat Index