Calculate Your Body Fat

Why Calculate Your Body Fat?

There may be medical reasons you'd need to track your body fat, but that'd be something ordered by your doctor. For this article, we'll assume you're a normal, largely healthy person simply interested in finding out what shape you're in. But that can be a great motivational force in and of itself.

Simply put, it's nice to see that your efforts are paying off -- and knowing that you lost X amount of fat over the past four weeks can be a distinct boost to your resolve when a friend pulls out a cold brewski or some gourmet chocolate ice cream.

It's equally useful when you're getting confusing feedback from the scale. Let's say you weigh yourself every 14 days, only to discover that you actually GAINED a pound since last time. What makes up that extra pound? Fat? Muscle? Water? If the first option, you're doing something wrong all of a sudden. The second option, you're in The Zone and are doing everything right. Third option, it'll likely pass soon enough. A second opinion can take the guesswork out of the equation, providing instant feedback.

Tape Measure and Math

You can go low-tech and use the old YMCA method employing only a tape measure and a basic math. Measure the waist just above the belly button.

For women, the formula is: (-76.76 + 4.15 x waist - 0.082 x weight) / weight

For men it's: (-98.42 + 4.15 x waist - 0.082 x weight) / weight

Needless to say, this is hardly exact, especially since it's very easy to (perhaps even unconsciously) suck in your gut a little more each time you test yourself.

Skinfold Pinching

One of the easiest methods is to get a specific caliper and measure a pinch of your waist. It is important to use the same spot and the same type of fold each time, but once you get the hang of things it'll be very quick. You can get these for as little as $10, but make sure to read the instructions carefully. They usually come with a chart indicating body fat percentages corresponding to the readout results. Another thing to check for is that it has a sliding marker that stops at the readout point, so you can check the results in a controlled fashion rather than try to read it glancing around your hands.

Bioelectrical Impedance Analysis (BIA)

Muscles are excellent electrical conductors, whereas fat is more insulating. This means you can run a tiny electric current through a person and get an approximation of the body fat percentage. Some scales have this as a built-in feature, and there are hand-held versions of the same, often in the price range of $100 or so. While quite convenient, bear in mind the word "approximation", as this is among the less reliable testing methods.

Water Displacement

If you're really serious, you can go to a professional and do a full test involving bone measurements and immersion in water. This will give you a lot more accurate number than a caliper or scale, but it's a one-shot only -- you need to cough up a couple hundred bucks again next month at your follow-up, and the month after that. There's an even more exact way to calculate your body fat that involves X-rays in addition to the water or air displacement, but that's well beyond the scope of this discussion. For a regular Joe or Jane, any of the preceding methods should be accurate enough to give a decent pointer about the general direction they're heading. Good luck!