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.


So the body fat percentage formulas are not as good as they could be.

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.

Here are some Q&A…

  • What does body fat percentage mean? Body fat percentage is simply the percentage of fat that your body contains. For your body to function properly it is important that your body contains a certain amount of fat.
  • How is body fat percentage calculated? Your body fat percentage is calculated by taking your age, height and weight, gender and waist measurement into account. There are many different forms on how to measure and calculate your body fat percentage. Your results will help you determine a healthy weight and realistic weight loss goals based on the information you provided.
  • What are some ways to measure body fat percentage? Skin fold caliper, bioelectric impedance analysis, anthropometric, hydrostatic weighing, or DEXA scan.
  • What are the body fat percentage basics? Body fat percentage, body fat distribution, body shape, age, muscle striations, and vascularity.
  • What is the body fat percentage for abs? The body fat percentage for nice abs is somewhere between 15% and 10%. Crazy bodybuilder-type-abs is around 7% and 3%.
  • What is the body fat percentage for bikini competition? A bikini competitor is anywhere from 8-13% body fat.
  • What body fat percentage is considered overweight? For women between ages 20-40, the overweight body fat percentage is between 33-39% and anywhere above 39% is considered obese. Women who are ages 41-60, the overweight body percentage is 35-40% and anywhere over 40% is considered obese. Whereas for men it’s a little bit different. Men between ages 20-40 overweight body fat percentage is between 19 and 25%, and obese is anywhere above 25%. Men ages 41-60, overweight is 22-27% and obese is anywhere over 27% body fat.
  • What does body fat percentage look like? As men gain body fat, the fat typically starts to go into the stomach area. As it grows, it will begin to form all over the body, but still mainly in the stomach. Wheres females, they typically see fat appearing into their hips and thighs. but women do see noticeable amounts of fat in their stomachs as well at even low body fat percentages.

Did you click on any faces or find other surprises?


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