Do body fat % calculators work?

tennisbabe94

According to the body fat percentage calculator on http://www.fat2fitradio.com/tools/mbf/ ,which was suggested to me by another MFP user, my body fat percentage is 17.7%. How accurate is this number? Can these calculators actually give a ballpark estimate or are they way off?

Also, if it is somewhat accurate, is 17.7% a healthy percentage? Is there anyone out there with a lot of knowledge on this stuff that would care to explain it? Thanks! :happy:

victoria4321

I don't think they work exactly. They work in the sense that if you use the same gauge consistently then seeing a difference with that will be beneficial to you. It's not a good method to class yourself as healthy or fit because not everyone has the same fat distribution.

For a real number its probably better to go to a lab.

MustBeTheRows

My understanding is that is based of the military formula which has been shown to be accurate to 2%. The only real way to be certain is several trips to a physiology lab.

contingencyplan

Use the same one three times within a 60 second period. Notice you'll get three totally different numbers that could be off each other by as much as 3-4%. There's your answer.

The one I have says in the instructions that for accuracy's sake, take three consecutive measurements and use an average of those three numbers.

tennisbabe94

Yeah I've noticed that! I thought it was weird how I got different numbers even though I plugged in the same data. :grumble: I'll definitely average the three.

missym357

It drove me crazy not knowing if they are accurate are not, so I had a dexa scan done- the online calculators were not accurate for me. They were off by 3-5 percentage points, which I consider significant. The only very close measurement I had was a caliper reading from a trainer.

tennisbabe94

I'll take it all with a grain of salt and go to a lab as well for the real deal!

supplemama

Also, if it is somewhat accurate, is 17.7% a healthy percentage? Is there anyone out there with a lot of knowledge on this stuff that would care to explain it? Thanks! :happy:

I read somewhere that for women of reproductive age 18-21% body fat is optimal. But if you're not trying to have a baby it probably doesn't matter.

ETA: Looks like you are at athlete level of body fat percentage:
http://en.wikipedia.org/wiki/Body_fat_percentage#Typical_body_fat_amounts

DakotaKeogh

I used several online ones and then finally got in the immersion tank. The tank showed the online ones were several points high. I was already at my goal % and didn't know it.

goldfinger88

I've found most to be very inaccurate. Most are far too low. I have two BIA (Bio-Electrical Impedance Analysis) tools at home. One are scales and the other handheld. I find the handheld, when used after I've been hydrated in the morning, is quite accurate. When I plug in the figures in the military body fat calculator, it's just about the same --- very close. But, it's still a bit too low in my opinion.

Despite the fact the fat2fit calculator takes your body frame into consideration, it's way too low. I find even the military calculator to be about 2% too low. So, I wouldn't put much faith in them.

As for your own body fat, it depends on your gender, age, frame and other variables. Calipers are the most accurate measurements next to under water testing. After those tests, BIA (Bio-Electrical Impedance Analysis) is reasonably accurate but not totally accurate.

It's all just an estimate unless you get under water testing.

noveltyaddict

Agreed. As I understand it, the more extreme you are at either end in terms of muscle and fat (athletic vs. overweight) the worse the estimate will be. For example, if you are a busty woman with a small waist, your body fat % will be higher, but there's not much you can do about the bust if you're not overweight elsewhere. Women need a certain amount of bodyfat to menstruate and bear children, which varies from person to person, but I think 30% is generally accepted to be the upper limit of healthy.

The most accurate measurement (apart from the specialized lab environment people are talking about--I'm not sure what they do there) is to use the immersion-tank method, where they measure your body volume as you displace water in a big tank and compare it with how much you weigh. I heard some health and fitness-product stores like GNC will have this apparatus and do it for you for free, but I've never seen one.

The bioelectric impedance method (like on a scale) is approximate but it will give you a ballpark. I think the taping method you did online might be better.