Sourced from:http://www.impulseadventure.com/weights/skinfold.html
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Whether you are trying a new gainer diet, cutting up, or just
curious, it's often a good idea to get a bodyfat measurement done.
There are various methods in use, and some are far better than
others. In order of decreasing accuracy:
* Autopsy
Extremely accurate. The physician seperates your fat from other
tissues and weighs everything. Fairly inconvenient, as it requires
you to be dead.
* Hydrostatic Weighing ("Dunk Tank")
Requires the individual to expel all their air underwater.
Expensive and difficult to locate a suitable facility.
* Skinfold Measurements
By far the most common method and is generally accurate to within a
few percentage points. Cheap (usually about $5 to get the test done
at a reputable fitness center). More detail on this method,
below.
* Bioelectrical Impedance (BIA)
These devices pass a small current between either your hands or
feet and determine the effective resistance. From this, and a host
of assumptions about the conductivities of various body tissues,
they try to determine the percentage of body fat. Some bathroom
scales even include this ability but one should be very skeptical
of the unit's accuracy. Some people have reported wildly-varying
results with these, although some manufacturers claim high
correlations with skinfold or underwater weighing results. Very
dependant upon your state of hydration.
* Infra-red (IR)
Infra-red measurements are made at your finger, and through some
magic, they attempt to determine your body fat composition. Very
inaccurate, but convenient and fast.
* Generalized Formulae (waist, height,
weight)
Numerous studies into the anthropometry of various individuals have
been compiled into tables that include the person's weight, height,
waist and actual bodyfat (generally done via skinfold
measurements). A simple linear prediction formula is then created
that fits loosely to the average population. These are very easy to
use, and cost you nothing, but they should only serve as a very
rough estimate. A section below details a few of these
formulae.
Generalized Equations
Equation 1:
For men: Bodyfat = -98.42 + 4.15*waist - .082*bodyweight
For women: Bodyfat = -76.76 + 4.15*waist - 0.082*bodyweight
NOTE: "waist" is in inches, "bodyweight" is in pounds.
Both formulae will give you the total number of pounds of bodyfat,
not your percentage. To get your percentage, divide the result
above by your total body weight.
