Body Fat Calculator

Body Fat Calculator

The best way of measuring your progress in losing fat and gaining muscle is to use an inexpensive skinfold caliper in conjunction with an accurate scale. Measure your skinfold thickness, then enter your values into the calculator and it will calculate your lean body mass (muscle weight) and your bodyfat percentage. These are the numbers that indicate your success!

Skin Fold Measurement Locations                                             
  1. All measurement should be made on the right side of the body
  2. Caliper should be placed 1 cm away from thumb and finger, perpendicular to skinfold, and halfway between crest and base of fold
  3. Pinch should be maintained while reading the caliper
  4. Wait 1 to 2 s (and not longer) before reading caliper
  5. Take duplicate measures at each site and retest if duplicate measurements are not within 1 to 2 mm
  6. Rotate through measurement sites or allow time for skin to regain normal texture and thickness
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Step 1: Enter Your Gender
Step 2: Enter Your Weight
Step 3: Enter Your Age
Step 4: Enter Skinfold Thickness
Skinfold thickness location (1)
Skinfold thickness location (2)
Skinfold thickness location (3)
Step 5: Enter Your Height

Your Results

Line Imperial Metric
1 Body Fat Percentage

2 Lean Body Mass

3 Body Fat

4 Fat Free Mass Index (FFMI)

Interpreting FFMI (Fat Free Mass Index)  
under 17 low muscle mass (skinny)
19-20 average FFMI for an American or European college student
20-23 noticeably muscular
25.7 Steve Reeves (pre-steroid era BB champ)
over 26 steroid user (Clinical Journal of Sports Medicine 5(1995):223-28)

Note: FFMI measures fat free mass. At what level fat free mass someone will look muscular depends on their frame size. Someone with narrow hips, small wrists, and small knees can look very muscular at a FFMI of 20. The inverse is true also. Someone with a FFMI of 23 might not look muscular at all if they have really wide hips, big wrists, and big knees. The equations for FFMI can be found in this research paper. Note that the equation that is given in the abstract is not the most useful one, that appears in the full paper. FFMI = Kg/m^2 + 6.1(1.8-m) where m is the height in meters and Kg is the LBM in Kilograms.

How To Measure Skinfold Thickness

How Often To Measure

If you are trying to gain muscle, the way you track your progress is to weekly weigh yourself and measure your skinfold and chart your Lean Body Mass (line 2 above) – this is a direct indication of how much muscle you are adding!If you are trying to lose fat, do the same thing. Weekly measure your weight and your skinfold thickness and chart your Body Fat (line 3 above), this is a direct indication of how much fat you are removing! Also,watch your Lean Body Mass (line 2 above) to insure you are not losing muscle mass by too drastic a caloric reduction. To chart your progress use graphpaper or use my spreadsheet below:

Progress Chart

Remember, its hard to measure weight accurately and its tough to measure skinfold thickness accurately so don’t be alarmed if your bodyfat appears to fluctuate wildly. As you get the hang of measuring consistently, the wild fluctuations will start to become a gradual curve on your LBM charts. Just keep measuring weekly and after 8 weeks or so you will start to see the trends. If you are a math type and want to know how I calculate the bodyfat percentage, here are the equations.

Like everything on, this calculator is completely free. Lots of websites have calorie calculators that you have to pay to use but my free calculator here is even better! If this is not the best calorie calculator you have ever used, please contact me via facebook and let me know how I can make it the best calorie calculator anywhere on the internet – free or not! My goal is to provide information so that the poorest teen can get the information they need to build a great physique. The information available on this website for free is just as good as all those expensive books, just not quite as polished – but its free! :)

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