Some dude stole my shit, but nevermind

Body Fat percentage Formula

Comments and Admiration of a body fat percentage formula

The body fat percentage formula, using your BMI, age, and gender:

Child Body Fat % = (1.51 x BMI) – (0.70 x Age) – (3.6 x gender) + 1.4

Adult Body Fat % = (1.20 x BMI) + (0.23 x Age) – (10.8 x gender) – 5.4

using gender male= 1, female= 0.

There are other ways to find formulas for body fat.1 written by other scientists. Reference 1 is another place to look.


  1. Jackson AS, Stanforth PR, Gagnon J, et al. The effect of sex, age and race on estimating percentage body fat from body mass index: the Heritage Family Study. Int J Obes Relat Metab Disord, Jun 2002;26(6):789-96

David David
Thanks. The formula was exactly what I…nevermind.

Gretchen Gretchen

David David
I realized, I’m too lazy to use it.


There is a problem with this formula, and others like it. They are linear.

Tyler Tyler
The straight lines. The pink one is from the formula on this page.

Various Body Fat versus BMI formulas

But Body fat percentage has a curved distribution relative to body mass index, not linear.
body fat versus BMI

Dr. Halls Dr. Halls
If you were a slim woman with BMI under 20, the pink line formula would say you had 25 to 30% body fat, which is totally wrong.

Talking Moose Talking Moose
I’d guess about 15 percent, from the curvy chart above.

Dr. Halls Dr. Halls
That formula is even on wikipedia. The world needs something better.

Betty Betty
That DOES make me mad, when I use online fat calculators.


January 20, 2015 update. A crazy thing I discovered. Someone copied my paragraph and pasted it into Yahoo Answers, and now when I search Google for that paragraph, it only shows Yahoo answers, and not my own page. So the more powerful domain wins, and my page gets penalized as duplicate content. That sucks. And they didn’t even give this page a link. Please don’t do that in the future. Just link here instead please. Each page that is penalized by google, weighs down the entire website.

Lets rephrase the question. If you know your BMI, do you also know your body fat percentage? The answer is yes, but only if you are kindof average in all respects. The above formula works, if you are average height, average weight, age around 30.

Is Body fat a better measurement than body mass index? YES. yes. well, maybe, It’s a coin toss.

A Like would be nice, or Share. For every like, I hear a bell, and smile, and you get wings.


End of page Navigation links: Return to category: Body Fat.  or  Back to top