Body Fat Calculator

Body fat percentage is the proportion of your body weight that comes from fat. The rest is made up of muscle, bone, organs, water and other non-fat tissue. It's a better reflection of health and fitness than just weight or BMI because two people who weigh the same can have very different amounts of body fat.

This calculator estimates body fat percentage using three methods and shows the corresponding standard classification.

What is body fat percentage?

Fat not only fills the body; it stores energy, protects organs, insulates against cold and supports the production of hormones that regulate appetite, metabolism and reproductive function. A small amount is essential fat required for life and health but what matters is how much fat is stored relative to lean tissue.

Too much fat, especially around the abdomen, increases your risk of heart disease, type 2 diabetes, high blood pressure and various cancers. Too little can also cause problems ranging from hormonal imbalances to a weakened immune system. The healthy range is between these extremes, and it differs for men and women because women are naturally predisposed to store more essential fats.

How to use this calculator:

Select a method, choose your gender and enter the required measurements. The body fat percentage is displayed as an easy to read number along with a color coded description that indicates classification and a breakdown of fat mass and lean mass. If you select the Target Weight option and enter a value, it will calculate what target weight would be needed in order for you to meet your goals. A graph compares results against each category range and displays weight in separate sections for fat and lean tissue.

Three methods.

The trade-off between accuracy and ease of use varies by method. Pick the one that will give you accurate data for your needs.

US Navy methodThis method uses a tape measure and is the most accurate option for home use, and used as standard in many calculation tools. Men input their height, neck circumference, and waist size; women also need to input hip size. The formulas use inches.

You can input either centimeters or inches and the calculator will convert between them. For example, if a man has a waist size of 34 inches, neck size of 16 inches, and height of 70 inches, then subtracting his neck from his waist gives him 18 inches, which calculates to about 15.5 (percent) body fat.

Lets take another example:

The calculation turns out as follow and the body fat percentage yield is around 19.9%

BMI method This method uses the Deurenberg formula to estimate body fat percentage based on Body Mass Index (BMI) and age. The input is easiest as only weight, height, and age are required but accuracy is lower for muscular or very thin individuals.

Here 1 stands for men and 0 for women. The BMI is calculated by dividing the weight (in kilograms) by the square of the height (in meters).

The relative fat mass (RFM) is a measure of...It is a relatively new estimation method that only requires height and waist circumference. As it is based on ratios the units cancel out so it can be used with any unit system.

Classification of body fat.

Body fat is divided into different ranges depending on gender. The table below uses the American Council on Exercise's widely accepted classification criteria. It is more important to know what range you fall in than it is to focus on a single number, as even with healthy lifestyles people can be both fit and average.

Fat content, fat-free mass, and FFM (fat-free mass index).

When body fat percentage and weight are known, a calculator will split the weight into fat mass and lean mass. Fat mass is found by multiplying the weight by the body fat percentage, while the remaining amount is lean mass. It can be more helpful to track these values over time than just looking at the numbers on the scale, as it's possible for body composition to improve even if there isn't much change in weight, since losing fat and gaining muscle can happen simultaneously.

The Fat Free Mass Index (FFMI) is calculated by taking the fat free body mass and dividing it by the square of your height. The calculation method is the same as BMI, which uses total weight. It's a measure of how much muscle mass you have relative to your height. Most men will be between 18-20, most women are between 15-17. Trained athletes will usually be higher than that.

Target weight

If you have a specific body fat percentage goal, the Target Weight option can estimate the weight required to achieve that body fat percentage. This is based on the assumption that your current lean body mass will be maintained and only fat will be reduced.

The target weight is calculated by dividing your lean body mass by the percent remaining after subtracting your desired body fat percentage. For example, if your lean body mass is 154 pounds (70 kg) and your desired body fat percentage is 15, then your target weight would be approximately 182 pounds (82 kg). Actual results may vary. Usually the lean body mass also changes slightly but this result can serve as a useful guideline for planning.

Measuring methods for optimal results

Using a tape measure, use a flexible measuring tape and hold it horizontally while holding it tight to the skin. Be careful not to press into the skin though. Men should measure their neck size below the Adam's apple and their waist size at the belly button position. Women should measure their waist size at its narrowest point and their hip size at its widest point. Take two or three measurements, average them out, and take your measurements at the same time every day to track it consistently.

What is possible with these estimates and what isn't.

All of the methods described here are estimates and not laboratory tests. If you do the measurement in a hurry there can be errors of several percentage points when using a tape measure. In addition, the results are less accurate for very thin people, those with highly developed muscles, and older people because they assume that fat distribution is typical. The BMI method inherits the weakness of BMI, which is its inability to distinguish muscle from fat. Gold standard methods such as DEXA scans, underwater weighing, and Bod Pods are more accurate but must be done in a doctor's office. If you use these methods regularly pick one method and track trends rather than over interpreting individual numbers.