Before you use the formulas, there are two measurements that are required:
Measurement 1: Bodyweight
Measurement 2: Waist Girth (measured at the umbilicus)
1) Multiply your bodyweight by 1.082. Add the result to 94.42. Once your calculation is complete, save the number. à (Bodyweight x 1.082) + 94.42=Result 1
2) Multiply your waist girth by 4.15. Once you get this result, subtract it from the number obtained in step 1 (ie: Step 1 result-Step 2 result). The result obtained after the subtraction is done is your lean bodyweight (your weight if you had no fat in your body at all). à Result 1 - (Waist Girth x 4.15)= Lean Body Weight
3) Finally, subtract your lean bodyweight from your total bodyweight (Total weight-Lean Bodyweight). Once you get the result, multiply that number by 100. Once you get the result divide it by your total bodyweight. This final result is your percentage of body fat. à ((Total Bodyweight - Lean Bodyweight) x 100) divided by (Your Body Weight) = Your Percentage of Body Fat.
I weigh 190 and I have a 30.5inch waist. Therefore, step 1 is (190 x 1.082) + 94.42 = 300. Step 2 says that my lean body weight equals 300-(30.5 x 4.15)=173.425. Finally, Step 3 says that my body fat percentage is ((190-173.425) x 100) divided by 190= 8.72%.
Before you use the formulas, there are five measurements that are required:
Measurement 1: Bodyweight.
Measurement 2: Wrist Circumference (measured at the widest point).
Measurement 3: Waist Circumference (measured at your umbilicus).
Measurement 4: Hip Circumference (measured at the widest point).
Measurement 5: Forearm Circumference (measured at the widest point).
1) Multiply your bodyweight by 0.732. à Bodyweight x .0732 = Result 1.
2) Add the result above to 8.987. à Result 1 + 8.987= Result 2.
3) Divide your wrist circumference by 3.14. à Wrist divided by 3.14 = Result 3.
4) Multiply your waist measurement by 0.157. à Waist x 0.157 = Result 4.
5) Multiply your hip measurement by 0.249. à Hip x 0.249 = Result 5.
6) Multiply your forearm measurement by 0.434. à Forearm x 0.434 = Result 6.
7) Add results 2 & 3. à Result 2 + Result 3 = Result 7.
8) Subtract Result 4 from Result 7. à Result 7 - Result 4 = Result 8.
9) Subtract Result 5 from Result 8. à Result 8 - Result 5 = Result 9.
10) Add Result 6 and Result 9. The result is your lean body mass (your fat free weight) à Result 6 + Result 9 = Lean Body Mass.
11) Subtract your lean body mass from your bodyweight. Once you get the result, multiply that number by 100. Once you get this result, divide it by your bodyweight. à ((Bodyweight-Lean Body Mass) x 100) divided by your bodyweight.
A woman that weighs 125, and has a wrist measurement of 6.0, a waist measurement of 24, a hip measurement of 38, and a forearm measurement of 9.5 would calculate her body fat percentage in the following manner. Step 1: 125 x 0.732=91.5. Step 2: 91.5 + 8.987=100.487. Step 3: 6 divided by 3.14=1.91. Step 4: 24 x 0.157=3.768. Step 5: 38 x 0.249=9.462. Step 6: 9.5 x 0.434=4.123. Step 7: 100.487+1.91=102.397. Step 8: 102.397-3.768=98.629. Step 9: 98.629-9.462=89.167. Step 10: 4.123+89.167=93.29 (Lean Body Weight: Fat Free Weight). Step 11: ((125-93.29) x 100) divided by 125 = (31.37 x 100) divided by 125 = 3171 divided by 125= 25.368 (Body Fat Percentage).
Notes: The formulas above are just approximations. The goal here is to have a point of reference from which to work. I recommend that you measure your body fat every three weeks. If you see a pattern where you see yourself gaining muscle and losing fat, then you know your program is right on track. If not, examine which part of your program is not optimal. Assuming that you are following an effective training routine, look at the things that could be going wrong such as you are not getting enough rest at night or more likely you are not following your nutrition plan to the letter.