My body fat %

Ang8178
Ang8178 Posts: 308
edited September 20 in Health and Weight Loss
OK first off, today is a rest day for me, and you guessed it, I sit on the computer and look up weight related stuff I've always wanted to know more about :laugh:

I've found sites you just put your measurments into and they caculate it out for you, but me being the weirdo that I am, I needed to know how it works and what formula they were using. I've done it 3 different times on 3 different web sites and once with my caculator. All of them were pretty close so I'm confident the % I got is close accurate.

:heart: :heart: 26.67% body fat :heart: :heart:

Sounds like an ok number to me. But I need to do some more "google" research to see if this is average or just awful for me :laugh:

Replies

  • jdelot
    jdelot Posts: 397 Member
    I'm not sure how tall you are, but that seems kind of high for someone under 137 lbs. I would question the calculations.
  • haleysman
    haleysman Posts: 48
    my scale checks mine by sending a current through my feet and uses some algebraic program to determine how much fat and water there is based upon resistance....kind of inaccurate depending on how hydrated one is, the best way i know of is to get weighed in and out of water and then they figure it that way
  • Ang8178
    Ang8178 Posts: 308
    OK my goal is to be at 20%. I'm 64 inches tall (5'4")
  • MacMadame
    MacMadame Posts: 1,893 Member
    There is no way an online formula can accurately tell you what your body fat percentage it. If you are getting similar results, it's because they are using pretty similar formulas, not because that number is accurate.

    For example, I had my body fat % done with calipers and it came out to 17%. This is probably slightly high as the calipers tend to over estimate body fat % on people who have lost tons of weight and have a lot of hanging skin. If you look at me, you'd think that was a believable number too. But the online formulas said my body fat was anywhere from 25 to 35%!! Um, I had (at the time) about 90 lb. of lean tissue and weighed 112. There is no way that I had even 25% body fat.

    I did find one site once that had you enter in about 15 measurements. That one did give a number that was closer to what my $300 Tanita Body Segmental Composition monitor was showing. But now I can't find the page any more. :sad:
  • Ang8178
    Ang8178 Posts: 308
    I can't beleive I'm going to type this all out, but this is the formula I followed. I don't know how numbers you divide and multiply by are made up, but here it goes.

    For women (men have far less todo)

    Measurements needed:
    Waist
    Hips
    Forearm
    Wrist

    1.) Body weight x 0.732= result 1

    2.) Add result 1 to 8.987= result 2

    3.) Divide wrist measurement by 3.14= result 3

    4.) Multiply waist measurement by 0.157= result 4

    5.) Multiply hip measurement by 0.249= result 5

    6.) Multiply forearm measurment by 0.434= result 6

    7.) Add result 2 and 3 together= result 7

    8.) Subtract result 4 from 7= result 8

    9.) subtract result 5 from 8= result 9

    10.) Add results 6 and 9= Lean body mass

    11.) Subract lean body mass from total body weight. Multiply by 100. Divide by total body weight= body fat %

    I know the most accurate is the water test, next would probably be the tape (that's what the military uses) and last is calipers.
  • haleysman
    haleysman Posts: 48
    what is the eqn for men, would be interesting to see how accurate my scale is?
  • Ang8178
    Ang8178 Posts: 308
    For Men:
    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.=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.

    Example:
    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%.


    http://www.davedraper.com/bodyfat-calculation.html

    Found the site I got the info from. I'd also like to know how accurate it is to your scale. Would let me know if mine was close to accurate :wink:
  • haleysman
    haleysman Posts: 48
    ok, just weighed and measured and did the math.....scale told me 28%, your formula said i'm 31%, so only a 3% difference, that being said i am 204 so that's somewhere between 57 and 63 pounds of fat. take that how you want
  • Ang8178
    Ang8178 Posts: 308
    I think for measuring, that's pretty close. I'm not buying an expensive scale (would if I could) or going to seek out a nutritionist for help, I'm ok knowing I could be under or over by 3%. Thanks for taking the time to compare :happy:
  • MacMadame
    MacMadame Posts: 1,893 Member
    The most accurate is actually a DEXA scan. It's the new gold standard. The dunk tank method can be thrown off by you not expelling enough air before you go under, but it's still the next best.

    But look at that formula... the only thing you input are your wrist, your waist , hip and forearm. There is no measurement of your legs or the two different sides of the body. (My left side is bigger.) Or your boobage -- it would give two people the same size except one is a D cup and one is an A cup the same body fat percentage! It can't possibly be accurate.

    If you want a cheap method, see if they'll measure you at the gym for free. Some will.
  • Iceprincessk25
    Iceprincessk25 Posts: 1,888 Member
    A lot of places have the bod pod that can measure body fat for you. All the universities around me have them and will measure your body fat for only $35.00
  • courtney_love2001
    courtney_love2001 Posts: 1,468 Member
    I was just doing this today :laugh: I knew it wouldn't be accurate, but I was curious, as I have one of those scales that supposedly "measures" the fat. My scale says 18% (yeah right) and the equations online say like 27%, which seems more reasonable to me. I'm just going to take it with a grain of salt....doesn't impact me I was just curious!
  • haleysman
    haleysman Posts: 48
    didn't really look all that close, but there was a machine on the wall at bally's that was $.50 and i think it measured bmi and %bf
  • MacMadame
    MacMadame Posts: 1,893 Member
    Sounds like it's using bio-imedience like my scale does.

    Well, BMI is just a formula based on weight and height. So it's just doing the math for you. I wouldn't pay 50 cents for that. You can use a free online calculator instead.
  • pettmybunny
    pettmybunny Posts: 1,986 Member
    So I just went through and did all the math. According to your formula, I have 27.61% body fat, with 132 lbs of lean muscle. I had a body composition test done this summer, and it had me at 35% body fat, with 117 lbs of lean muscle. I recently had a calipur test done (for an entry assesment) and it had me at 39% body fat (probably close, since I've put on 15 lbs since the summer test). I'm guessing your formula was wrong.

    The formula may be not be accurate because my idea of my waist (two inches above belly button) might be different from someone elses (directly at belly button). Same thing for hips, etc.
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