Your body fat levels are used as the basis of all kinds of calculations. Our calculators will do the hard work for you, but it's still important to understand some terms and background.

Your total bodyweight can be divided into two types of tissues:

Fat mass
Everything else; called lean body mass (LBM)

LBM (lean body mass) is an acronym we'll be using a lot so it's important to remember and understand that term. LBM is everything except fat tissues. It includes (among other things) muscles, bones, the organs, water, minerals, undigested food, feces and urine.

This is important to realize when you are tracking weight. Certain types of LBM, especially water, can fluctuate a lot. Read more about this in Weight Tracking. Ultimately, to lose weight -- at least the way you are probably thinking in your head as you imagine your body size shrinking and fat rolls disappearing -- you want to target FAT loss.

Estimating Your Body Fat

Method 1: Body Mass Index (BMI)

Traditional BMI is based on weight and height. So it accounts for the fact that taller people are expected to weigh more simply because they are taller, not because they're fatter. And shorter people naturally weigh less. However, it doesn't account for body composition or muscle weight vs fat weight; for example, athletic or very active individuals have more muscle (which weighs more that fat). At best BMI provides an extremely rough estimate.

Method 2: Jackson-Pollock Formula

This is also known as the Jackson-Pollock-Ward formula.

The formula for men is: 1.10938 - (0.0008267 x the sum of the chest, abdomen and thigh measurements in millimeters) (0.0000016 x the square of the sum of the chest, abdomen and thigh measurements in millimeters) - (0.0002574 x age) = body density

The formula for women is: 1.0994921 - (0.0009929 x the sum of the triceps, thigh and supra-iliac measurements) (0.0000023 x the square of the sum of the triceps, thigh and suprailiac measurements) - (0.0001392 x age) = body density

The resulting number measures body density, which is then plugged into another formula, the Siri equation, to get a body fat estimate. The formula is: [(4.95/body density) - 4.5] x 100.

Method 3: U.S. Navy Method

This method was developed at the Naval Health Research Center by Hodgdon and Beckett in 1984.

For men: Body fat percent = 495 / ( 1.0324 - 0.19077 * log10( waist - neck ) + 0.15456 * log10( height ) ) - 450

For women: Body fat percent = 495 / ( 1.29579 - 0.35004 * log10( waist + hip - neck ) + 0.22100 * log10( height ) ) - 450

Method 4: Body Fat Scales

These are the bioelectric impedance body fat scales, such as Tanita brand. The main problem is that hydration can affect the numbers quite dramatically. So if you take a big drink of water, or a large urination, the number changes. Likewise if you are on a diet where water weight fluctuates, this scale will be wrong. One idea is to record your measurements say twice a day at the same time (morning and night) and then average the numbers.

Method 5: Calipers [Most Accurate]

This is the most accurate method, and recommended if you are athletic/lean/active. You use these calipers to take various skin fold measurements. For example, this one: https://www.amazon.com/Accu-Measure-Fitness-Personal-Caliper-Measurement/dp/B000G7YW74/ You then use the charts provided in the instructions for the product to help you calculate an accurate percentage.

What is a Healthy BMI and Body Fat?

BMI Chart

This is a simple, standard BMI chart for your reference.

BMI	Description
Under 18.5	Underweight.
18.5 to 24.9	Healthy Weight.
25 to 29.9	Overweight (unless you are a lean, muscular person).
30	Obese (greatest disease risk).

Body Fat

There's a lot of controversy over what is a "healthy" body fat percentage. Our bodies naturally carry a certain amount of fat. Even competition bodybuilders or skinny marathon runners who look like they don't have an ounce of fat, actually do.

Numbers vary according to who you're talking to.

Take all these numbers with a grain of salt.

From the American Council on Exercise:

Description	Women	Men
Essential fat	10 - 13%	2 - 5%
Athletes	14 - 20%	6 - 13%
Fitness	21 - 24%	14 - 17%
Average	25 - 31%	18 - 24%
Obese	32%	25%

Note: Essential fat is the extreme lower limits of body fat that the body can have. It is the level that competition bodybuilders aim for and elite runners often have. Some research differs from the above chart and indicates it is 7-9% for women and 3-5% for men.

The chart above is a decent starting point but doesn't tell the whole story. A person who exercises can be more healthy than a person with the same body fat who doesn't exercise. Also, calling an athlete unhealthy because they have very low body fat is obviously not true. Finally, if you fall in the Average category you are considered Overweight on a BMI scale.

Ideal body fat is probably best represented by this chart, which is based on the "Jackson-Pollock Formula".

Age (Years)	Women	Men
20	17.7%	8.5%
25	18.4%	10.5%
30	19.3%	12.7%
35	21.5%	13.7%
40	22.2%	15.3%
45	22.9%	16.4%
50	25.2%	18.9%
55	26.3%	20.9%

Waist Size

Waist size is another indicator and is very simple. It's also great because waist measurement can't fool you like weight can (weight fluctuations).

Here's a basic rule: If your waist size is over 35 inches if you are a woman, or 40 inches if you're a man, it's a warning flag that you need to slim down.

Note that if you are carrying extra weight around your middle (meaning apple-shaped), you are at a greater risk of developing heart disease, stroke, diabetes and high blood pressure, even if your BMI says your weight is healthy.