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BF % Calculation

perpetual_injuries

By perpetual_injuries
in Gyms & equipment

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Dog Licker New member

Dog Licker

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The only one-site bf measurement I know of that is considered somewhat accurate, is for measurement taken at the iliac crest. So unfortunately what you have taken isn't at this site. In any case if you do take a measurement at the iliac crest then this document will give you the results as well as some references to how accurate the measurement could be http://tinyurl.com/4zhj5wy

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Phedder Veteran member

Phedder

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Don't take anything done by students, especially with only 2 sites, as accurate. The more experienced the tester, and the more sites taken, the more accurate it will be. I had a 3 site pinch test done in my exercise physiology class by another student at the start of last year that put me at 7.3% BF, wasn't any leaner (probably a bit fatter actually) than I am now and recently measured at 12.4% so being off by at least 5% is huge.

If you really want to know your bf% get someone experienced to do it and make sure it's at least 7 sites.

You're doing summer school I take it? Nutrition major or just doing it out of interest? Can't wait to get back to Otago myself, home's far more boring :lol:

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perpetual_injuries Junior member

perpetual_injuries

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Yeah i'm at summer school. Taking the paper out of interest, looking at going into med in 2012. All the study I've been doing on nutrition has made me want to specialise in something like sports med now :P

If you're talking about the scales that measure your BF% via electric resistance then I'll have to point out that these are monstrously inaccurate. If you just mean normal scales, then they have no way at all of working out BF%.

I've have professional 7 site and 4 site tests done. With my current body composition they both yield the same results. 4 is pretty accurate. Part of the reason I wanted to use the classes results was the cost. Free vs. god knows what for the pro to do it. Also we had two different people take the same measurement 3 times per site and eliminated the top and bottom extremes then averaged them. Not as good as a pro by any means, but should be at least modestly accurate.

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agent86 Member

agent86

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There is a big variation in fat distribution between people so where you do the pinch test matters a lot.

I hold most of my fat around the stomach and lower back. If I did my triceps and upper back then I would get a false result. In fact between competing and off season my triceps might vary by 2 mm but my stomach will vary by 20mm.

The caliper measurement method will always average out your readings. A very low reading from one site will lower the total and of course a very high reading will increase it.

I never try to work out a percentage as it is always going to be innacurate.

I measure the 2 sites I know are always the highest and try to reduce these. You can usually tell by looking in the mirror if you are overweight.

To answer your question 2 sites are a waste of time and 5 or more would be more accurate.

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nate225 Veteran member

nate225

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There is a big variation in fat distribution between people so where you do the pinch test matters a lot.

I hold most of my fat around the stomach and lower back. If I did my triceps and upper back then I would get a false result. In fact between competing and off season my triceps might vary by 2 mm but my stomach will vary by 20mm.

The caliper measurement method will always average out your readings. A very low reading from one site will lower the total and of course a very high reading will increase it.

I never try to work out a percentage as it is always going to be innacurate. I measure the 2 sites I know are always the highest and try to reduce these. You can usually tell by looking in the mirror if you are overweight.

To answer your question 2 sites are a waste of time and 5 or more would be more accurate.

I assume you mean because all the calculations come out slightly differently as all equation formulas have certain assumptions?

A better way (IMHO) than taking the two highest sites is to you a "sum of 8" type approach where you add all the measurements together getting a total skinfold measurement. Then look to decrease this number.

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agent86 Member

agent86

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Yes agree 8 sites added and then try to decrease is a great idea. Don't try to work out a percentage as these calculations are just an approximation.

I usually measure only 2 worst sites because I know what skinfolds need to be at these sites to compete. I know if these drop to a certain level the rest will be very low.

I do my own measurement, so usually only do the abdominal and then every few weeks get my workmate to check my lower back.

This way you don't have to pay every time you want all the sites checked.

There are some fairly cheap plastic calipers around and if you were doing a measurement you would take about 5 readings at one site and see what the most consistent reading is.

It doesn't matter how you measure as long as you do it the same each time and get a relative measure of fat loss.

I think too many people get caught up in percentages when they can vary so much between who measures them.

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perpetual_injuries Junior member

perpetual_injuries

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I'm a fan of the 4 site (as it provides the same results as 8 whenever i've done both) when doing skinfolds.

The question here was more to do with working with the limited info on 2 sites. It's pretty obvious it would be mostly useless.

I'm getting a DEXA scan done mid feb, so that's going to give me a very accurate BF%. I'll just wait to for that one.

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nate225 Veteran member

nate225

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Yes agree 8 sites added and then try to decrease is a great idea. Don't try to work out a percentage as these calculations are just an approximation.

I usually measure only 2 worst sites because I know what skinfolds need to be at these sites to compete. I know if these drop to a certain level the rest will be very low.

I do my own measurement, so usually only do the abdominal and then every few weeks get my workmate to check my lower back.

This way you don't have to pay every time you want all the sites checked.

There are some fairly cheap plastic calipers around and if you were doing a measurement you would take about 5 readings at one site and see what the most consistent reading is.

It doesn't matter how you measure as long as you do it the same each time and get a relative measure of fat loss.

I think too many people get caught up in percentages when they can vary so much between who measures them.[/quote]

:nod:

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  • 8 months later...
Phedder Veteran member

Phedder

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I hate to dredge up an old thread like this.....(Not Really)

But I am trying to find a reliable formula for working out Bf% once you have the Sum of 8. Anybody able to help?

Might want to specify what 8 sites to make sure you get the right formula :nod:

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HarryB Veteran member

HarryB

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OR OR OR OR OR OR you could just get some proper scales to stand on. You know, that would work too.

You're not implying that the scales that give your bf% are accurate? :?

They aren't completely accurate. But at least you'd know the bf% in your legs. Well roughly.

ermmmmm quite a few years ago approximately 4 days out from a comp where I had striated glutes (yeah I was super puny) I did one of those scales tests and it told me I was 18% bf. I could never credit one of those things as being useful.

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Optimass Veteran member

Optimass

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You're not implying that the scales that give your bf% are accurate? :?

They aren't completely accurate. But at least you'd know the bf% in your legs. Well roughly.

ermmmmm quite a few years ago approximately 4 days out from a comp where I had striated glutes (yeah I was super puny) I did one of those scales tests and it told me I was 18% bf. I could never credit one of those things as being useful.

only designed to test normal to active humans with close to normal levels of bfat. If you are under 6% they cant get a good read - also if you are taller than 5'11 this will also impact as the radio wave can only travel so far.

You need to test same time of day and under the same hydration and food conditions - i.e 2 hours after your last meal having taken the same amount of water (e.g 2L) at 1pm -- to get a bench mark. In saying that if you are in a normal fat range they are ok for bench marking LBM - but I would never rely on them...

Find find someone with a set of digital calipers. way more accurate than a standard pair. Or look for a comp test like contours in Albany use - cant remember what its called but its the same machine used in hospitals overseas ... said to be 99% accurate.

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