How to Calculate your Body Fat Percentage

Body fat, lean mass, fat free weight, body mass index; what do these words mean but even more importantly how do you use them to help you reach your fitness goals?

Body Fat and BMI ranges

A person’s body weight is composed of body fat and fat-free weight (or lean mass). Body fat is adipose tissue such as belly fat while fat free weight is made up of muscles, bones, blood, nervous tissue and organs. It represents the rest of the body’s weight not including the fat.

Generally a healthy body fat range for women is between 21-24% and for man it is between 14-17%. The difference in numbers is due to women requiring a higher body fat percentage in order to maintain menstruation and the ability to have children. Body Mass Index (BMI) adjusts weight in relation to height but its drawback is that many athletes and body builders would be categorized as overweight because of their weight in comparison to their height. BMI doesn’t consider if the weight is fat or muscle and its normal range is between 18.5 and 24.9 for both genders.

Measuring Body Fat and BMI

The easiest way to calculate BMI or body fat is by using a handheld body fat analyzer that costs less than $100. Body fat analyzer use harmless electrical current that pass through the body tissue measuring resistance since the current goes slower through fat than muscle. The resistance reading is then used in a formula to provide the BMI and body fat percentage reading. To avoid buying body fat analyzers and doing math calculations, a tape measure can be used. Stand up straight, hold snug without pulling tight and measure the waist just above the belly button. Measurements over 32 inches for women and 37 for men indicate increased health risks.

When trying to lose body fat, the accepted guideline is that individuals should lose no more than 1-2 pounds per week with a combination of diet and exercise. Exercise should be both cardio and especially resistance training to build up lean mass; otherwise about 25% of every pound lost will come from lean, calorie-burning muscles. Now that you better understand the meaning of body fat, how do you use it to reach your fitness goal? Let’s answer what is a reasonable weight, how much you need to lose to reach the desired body fat percentage, and how long should you expect it to take.

Body Fat Formula

Let’s use the example of a 49 year old male who weighs 212 pound and has a body fat of 21.3%. His goal is to reach the healthy male range of 17%. To figure out his weight in the optimal range, we need to first calculate his lean mass. Since he has 21.3 % of body fat, we know his lean mass is 78.7% (100-21.3). Multiplying his total weight by the lean mass provides us his lean body weight of 167 pounds (212 pounds x 0.787). For 17% body fat the lean percent is 83% (100-17). The last step to get the desired body weight is to divide the lean body weight by the desired lean percentage which equals 201 pound (167/0.83). To lower his body fat from 21.3% to 17%, this man needs to lose at least 11 pounds (212-201) which, at a rate of 1-2 pounds a week, will take between 6-11 weeks.

Healthy Body Composition

Diet alone won’t necessarily lead to huge decreases in body fat since weight loss without exercise will lead to decreases in lean mass as well. Maintaining a healthy body composition is an important part of a person’s wellbeing and body fat is a good indicator of how much of your body is composed of lean mass and how much is fat mass. But this indicator should be used to make sure you fall in the average range and not to stay below a certain range.

About the Author
Aris Akavan, ACE certified Personal Trainer & Lifestyle and Weight Management Coach, is owner of Body Fitness by Aris. Her mission is to assist others in leading a healthier lifestyle by balancing exercise and proper eating habits to achieve the ultimate body & mind wellness. Aris leads by example as she practices what she preaches. She leads an alcohol free and smoke free lifestyle and has worked out while following proper nutrition practices for over 10 years. In the last few years she also started participating in 5k races, adventure runs and triathlons. You can visit Aris at any of her following: