BMI to body fat %

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Merkavar
Merkavar Posts: 3,082 Member
in Health and Weight Loss
so I just came across this formula which seems to line up with the % from my scale for body fat %.

Just wondering if it's accurate for others.

Anyone mind calculating this and posting the result, along with what you think your body fat % actually is.

Formula is
1.2xbmi + 0.23xage -5.4 for female and -16.2 for males.

See my scales and this formula are 1.4% different.

Just curious as to the accuracy of this formula.

I might post a image of me working out as a reward :P
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Replies

  • shadow2soul
    shadow2soul Posts: 7,692 Member
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    The formula gave me 27%. My scale gives me approximately 25%. Actual BF% is unknown.
  • lorrpb
    lorrpb Posts: 11,464 Member
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    1% is pretty darn close for something that's just a ballpark estimate.
  • Merkavar
    Merkavar Posts: 3,082 Member
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    lorrpb wrote: »
    1% is pretty darn close for something that's just a ballpark estimate.

    That's what I thought. I'm guessing its limitations would be similar to BMI where muscular people are treated like they are over weight.
  • 6502programmer
    6502programmer Posts: 515 Member
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    I come up with 30% on this, but my scale says 28. I don't know if my scale is entirely accurate, as that puts my LBM on a 5'11 body at 160 pounds.
  • LadyLots2Lose
    LadyLots2Lose Posts: 110 Member
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    I don't have scales that measure body fat % so, I compared the result of the formula (I got 36.71%) with the body fat % result from the DEXA scan I had in February (25.3%) which is a variance of about 11.4%. Not sure if that helps or not though. It seems I still have a fair way to go.
  • tomatoey
    tomatoey Posts: 5,459 Member
    edited August 2015
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    It's within 2% of what I get on various scales and calculators, and I think it's very close from visual estimation.

    ARgh ok ok - bmi = 21.1, bf% via your formula = 28.89; I got between 28 and 30 on those scales, last time I checked, a couple of pounds ago. (Yeah I know it's within the average range. Not where I want to be :/)
  • senecarr
    senecarr Posts: 5,377 Member
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    Formula gives me 27.51%. If I take my DEXA scan lean body mass from about 2 months ago (I've lost some weight since then) and use it with my current body weight, I'm 29.35%.
  • PAV8888
    PAV8888 Posts: 13,658 Member
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    I have four DXA scans and a useless Bio-impedance scale to add to the mix:

    BMI 34.5 Body Fat: 38.8% Aria Scale: N/A Your Formula: 36.47%
    BMI 31.2 Body Fat: 32.9% Aria Scale: 26.4% Your Formula: 32.51%
    BMI 29.4 Body Fat: 29.3% Aria Scale: 24.1% Your Formula: 30.23%
    BMI 26.7 Body Fat: 27.3% Aria Scale: 21.9% Your Formula: 27.83%
  • Asher_Ethan
    Asher_Ethan Posts: 2,430 Member
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    Gives me 28.02.... I've always felt I was 25% - 20%... I have no way of actually knowing though.
  • yellowantphil
    yellowantphil Posts: 787 Member
    edited August 2015
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    Merkavar wrote: »
    Formula is
    1.2xbmi + 0.23xage -5.4 for female and -16.2 for males.

    That formula says I’m 13.3%. Looking at the formulas at Strength Unbound, the YMCA modified and PN&F formulas both give around 13%. I imagine that that number is fairly close to my real body fat percentage, but I don’t know.
  • vismal
    vismal Posts: 2,463 Member
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    Gave me 22.6, not even close.
  • ahoy_m8
    ahoy_m8 Posts: 3,053 Member
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    Gave me 28%. I think I'm <20%. Your formula seems to punish age.
  • Merkavar
    Merkavar Posts: 3,082 Member
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    vismal wrote: »
    Gave me 22.6, not even close.

    Too high?

    Got a bunch of muscles? What do you think you % is?
  • Hornsby
    Hornsby Posts: 10,322 Member
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    Gave me 21.59. Not even close.
  • boogiewookie
    boogiewookie Posts: 206 Member
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    I calculated my bf% online using a bunch of physical measurements, plus my weight and height. that number (which is too high to mention lol) only differs by a fraction of a percent.
  • Merkavar
    Merkavar Posts: 3,082 Member
    edited August 2015
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    So far it seems fairly accurate except for people with avatars of very strong looking people.

    Here is an image of me working out. As thanks for helping me see how accurate the formula is. Enjoy :P
    soxvgit1hjnu.jpg
    Got to be able to have a little fun.
  • yellowantphil
    yellowantphil Posts: 787 Member
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    Merkavar wrote: »
    So far it seems fairly accurate except for people with avatars of very strong looking people.

    I imagine that it’s also inaccurate for somewhat older people who try to stay fit. The formula assumes that your body fat percentage increases with age, but I’m sure that there are some counterexamples to that on this site.

    Still, it’s interesting how close it seems to be for someone with an average build.
  • dondotwinks
    dondotwinks Posts: 93 Member
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    I got 38.8% my scales this morning gave me 39.3%. Pretty damn close
  • Sued0nim
    Sued0nim Posts: 17,456 Member
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    Merkavar wrote: »
    so I just came across this formula which seems to line up with the % from my scale for body fat %.

    Just wondering if it's accurate for others.

    Anyone mind calculating this and posting the result, along with what you think your body fat % actually is.

    Formula is
    1.2xbmi + 0.23xage -5.4 for female and -16.2 for males.

    See my scales and this formula are 1.4% different.

    Just curious as to the accuracy of this formula.

    I might post a image of me working out as a reward :P

    How does that take account of musculature which is a pre-requisite for understanding BF isn't it?
  • Sued0nim
    Sued0nim Posts: 17,456 Member
    edited August 2015
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    Without meaning to be smug that gives me a BF reading of 34.2

    That's out by around 10-11%

    I don't think I am a "very strong looking person", although I am old and relatively fit I suppose

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