How to Calculate Body Fat Using Waist Measurement & Weight

bodyfat
calculation
formula
#1

I was interested in trying to figure my present percentage of bodyfat based on a mathematical formula I found in an article by someone with an AA in exercise science - but I can’t even input the formula in a calculator and have it turn out right.

Can anyone help simplify how one does this formula with a calculator? I figured the stuff in parentheses, then used those sums in the formula - but it is saying my bodyfat % is 15.5% or something which can’t possibly be right, it’s more like 20-25% (I’m not smaller than I was in my 30s, etc). So I must be doing the formula wrong.

Women’s formula: 163.205 - (waist + hip - neck) / 100 - 97.684 x (height / 100) - 78.387.

My first parentheses totals 67, second one is .70

Men’s formula: 86.010 - (waist - neck) / 100 - 70.041 x (height / 100) + 36.76. The result determines your percentage of body fat.

Is this a legit formula? I wanted to solve it but it’s driving me mad now so maybe will just ignore it. Being that it’s from digital media content, it may just be wonky.

Got it from this article: https://healthyliving.azcentral.com/calculate-body-fat-using-waist-measurement-weight-1389.html

(Ron) #2

SBM,
Are you subtracting the neck measurement as suggested in your post? You need to add all three measurements together.

edit - no that isn’t right either. Will keep playing with it :thinking:

I give up - the formula for women isn’t right somehow. I run my numbers in the men’s formula and it is within .7 of what my BF number has reduced to with weight loss from the last time I had a scan, but cannot get your numbers to work with the woman’s formula either.

(Shayne) #3

It looks like the formula for the Navy bodyfat method. I Googled it and use one of the online calculators for comparison to what my scale says. I like the Navy method just because I was in the Navy and so I’m familiar with it.

(Bacon is a many-splendoured thing) #4

I tried the men’s formula, and apparently I am 74% body fat. Guess I’ll be very thin once I’m done losing!

I also wonder why they have you start with 86.01, subtract something, subtract something else, and then add back 36.76 at the end. Why not just start with 122.77 and do the subtractions?

(Raj Seth) #5

I call BS on that. probably a typo somewhere. If the formula for men is
86.010 - (waist - neck) / 100 - 70.041 x (height / 100) + 36.76
Then losing 12 inches on the waist lowers your BF by 0.12%. Yeah right!
Its basically 120 - 70% of height in inches. no relationship to anything meaningful in that form. maybe missing parentheses

(Bacon is a many-splendoured thing) #6

Here are the U.S. Army formulas.

For men, %BF = [ 86.010 * log10( waist – neck ) ] – [ 70.041 * log10(height) ] + 36.76

For women, %BF = [ 163.205 * log10( waist + hip – neck ) ] – [ 97.684 * log10(height) ] – 78.387

Whew! Now I’m only 29% body fat.

ETA: And now I’m wondering how the woman who wrote that article got the idea that log10(x) = x/100

(Raj Seth) #7

@PaulL misinformation on the inter web - how could that be??? :joy:

#8

OK, thanks everyone. Relieved to know that formula was wrong because I sure tried to figure it.

That U.S. Army formula looks like fun to try @PaulL - I know an asterick means ‘multiply’ but I don’t know what the heck log 10 is !?!?

How does a human being who never studied logarithms input this into a calculator? :rofl: I found an online calculator that offers a ‘log’ button, so that’s progress at least, I guess lol.

(Bacon is a many-splendoured thing) #9

@SlowBurnMary It depends on your calculator, unfortunately. In the Windows 10 calculator app, you type in the number first, then click “log,” and the result is the log base 10. And the only way I know that is from trying. If you use a number that is a power of 10, the result will be an integer, so it’s not that hard to figure out if you’re doing it right.

The definition of logarithm to the base 10 is “the power of ten that yields the number in question.” So log(100) is 2, log(1000) is 3, log(2) is 0.30103, etc. It is possible to have logarithms to other bases, as well. (When the context is clear, mathematicians will generally omit the subscript, so be careful!) The most commonly-used logarithms are actually the so-called “natural” logarithms, commonly written loge or nlog, for people who are too busy to write subscripts. (The transcendental number e arises from the calculation of compound interest and was given its name in honor of Leonhard Euler.)

The Windows 10 app doesn’t seem to have a natural log function built in, which is funny, because the Windows XP calculator had both loge and log10. (Of course, XP was a real operating system; 10 is just the same backbone gussied up to look trendier.)

#10

Very interesting stuff! OK, will go about trying to rework it on an online calculator this week. I never got to logarithms in school, but now I have keto-brainz which should help it get transcendental! :smile: