STEP 1 Know the ranges for women 了解女性的大致范围

Know the body fat ranges to aim for if you're a woman. 10 percent body fat is the absolute minimum; athletes tend to be in the 14 to 20 percent range. Fit people are at 21 to 24 percent. 25 to 31 percent is acceptable, and 32 percent and higher is too much.

STEP 2 Know the ranges for men 了解男性的大致范围

Know the body fat ranges to shoot for if you're a man. For men, 2 to 4 percent is essential, athletes are 6 to 13 percent, fit men are 14 to 17 percent, and 18 to 25 percent is considered acceptable. 26 percent or more is considered excessive.

STEP 3 Avoid water and exercise 避免过多饮水及运动

Prepare for taking your measurements. Don't drinking too much water or exercise 2 hours before taking measurements as this can skew the body fat percentage scores.

STEP 4 Locate measurement sites 定位测量点

Locate the sites for skin-fold measurements. For men, the sites are diagonally on the chest, and vertically on the abdominals and thighs. For women, the sites are vertically on the triceps and thighs, and diagonally on the suprailiac, which is midway between the hip joint and the rib cage.

STEP 5 Use a caliper 使用卡尺

Use a caliper to take skin-fold measurements. Pinch and pull a fold of skin using your index finger and thumb. Use the caliper to take a measurement one centimeter away. Wait a few seconds for the fat to compress. Take the measurements from your right side, and take two from each site.

Have a trained professional take skin-fold measurements to get the most accurate numbers.

STEP 6 Calculate your body density 计算身体密度

Add your skin-fold measurements, and enter the sum into the body density equation to calculate your body density. For women, the equation is .0000023 times the sum squared, minus your age multiplied by .0001392, minus .0009929 multiplied by the sum, plus 1.0994921. For men, the numbers are .0000016, .0002574, .0008267, and 1.1093800.

STEP 7 Determine body fat percentage 判定体脂百分比

Determine your body fat percentage by dividing 495 by your body density and subtracting 450.

To avoid number crunching, use an online calculator to determine your body density and fat percentage based on your skin-fold measurements.

STEP 8 Take a bioelectrical impedance analysis 采用生物电阻抗分析法

Take a bioelectrical impedance analysis using a fat-percentage scale if you want to bypass the math. The scale sends a low-voltage electrical current through your body to measure your fat percentage. Electricity goes faster through fat-free mass like muscles.

STEP 9 Understand the error rate 了解错误率

Understand that the error rate for these methods can be as high as 8 percent, but your body fat percentage range will give you a good idea of your body makeup and what goals you should aim for. Now you know your body-fat percentage, and can set accurate goals.

According to the Centers for Disease Control, Mississippi had the highest obesity rate in 2009 at 34.4 percent.