Body Fat Calculator

Body fat percentage is one of the important indicators of health. Several metabolic syndromes, malabsorptive disorders, and systemic diseases are associated with both excess (obesity) and deficiency of adipose tissue (body fat).

To stay healthy and fit, calculating body fat percentage is crucial to achieve the ideal levels of adipose tissue (based on your age, gender, weight, height, and activity level).

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In this post, we will explain the working of a body fat calculator, as well as how you can use it to your advantage to set and attain your fitness goals.

What Is Body Fat?

Fats are fuel sources or energy reserves of the body. Medically known as adipose tissue, body fat is made up of several small units called fatty acids.

It extends throughout your body, primarily occurring under the skin (subcutaneous fat), between the internal organs (visceral fat), and within the bone cavities (bone marrow fat).

Body fat is classified into two types; essential body fat and storage body fat:

Essential Body Fat

Body fat that is required to support normal physiological functions is called essential body fat. It is found in bone marrow, nerve tissues, and within the membranes of viscera (organs).

Essential body fat plays a critical role in hormone regulation. Hormones are regulatory chemicals that maintain general physiology. Therefore, essential fat is important for fertility, vitamin absorption, temperature regulation, etc.

Unlike some other types of fats, essential fats are not synthesized in the body and, thus, come exclusively from food. Sunflower oil, sesame and pumpkin seeds, walnuts, fatty fish, soymilk, and walnuts, are some of the common sources of essential body fat.

Although the percentage of essential fat depends on your diet, it typically constitutes 3% of total body weight in men and 12% in women.

Storage Body Fat

Fats serve as an important energy source for the body. They are one the most energy-efficient cells, as a gram of fat metabolizes into nine calories.

Storage body fat is simply the fat that is reserved to be used for energy at the time of calorie deficit or in a fasting state. Most of this fat is found under the skin in adipose cells.

This storage body fat is sourced from food, as well as synthesized within the body. The excess protein and carbohydrates that you eat are processed in the liver into fats, which are kept for later use.

Importance Of Body Fat

While body fat is typically associated with obesity and poor health, it is, in fact, very important to sustain a healthy and long life.

Energy Reserve

Providing energy in the case of calorie deficit is one of the most important roles of body fat. When proteins and carbohydrates are not immediately available, the liver breaks down stored fat into special molecules called ketones. These ketones are then used for energy.

The dietary fat (essential body fat) is also broken down in the liver into fatty acids and glycerol, both of which fulfill your energy requirements.

Vitamin Absorption

Body fat is integral for vitamin absorption. Four fat soluble vitamins are found in the diet; Vitamin A, D, E, and K.

  • Vitamin A or retinoic acid is required for vision, reproduction, immune system, and growth. It also helps keep the vital organs (lungs and heart) working efficiently.
  • Vitamin D regulates calcium absorption in the body, which helps maintain bone density and strength. Therefore, a deficiency of vitamin D poses a risk of brittle, weak bones, osteoporosis, arthritis, and several other complications.
  • Vitamin E is great for skin health. It prevents free radical damage, in turn enhancing skin glow and healing inflammation.
  • Vitamin K forms proteins required for coagulation (blood clotting). This is why low levels of vitamin K result in excessive blood loss and hemorrhage.

Cognitive Development

Cognitive development and growth have strong links with body fat. Essential body fats, like Omega-3 and Omega-6, are crucial for proper brain growth.

Therefore, inadequate intake of these two essential fats is associated with brain fog, memory loss, general fatigue, and other related problems.

Ensuring proper intake of fat-rich foods like fish oils, especially in children, can improve cognitive abilities.


Body fat sourced from olive oil, peanut oil, canola oil, avocados, nuts, and seeds, helps build immunity. Research shows that high body fat percentage is associated with an increase in T helper cells (important immune cells) which helps prevent diseases.

Sexual Activity

Sexual activity and libido are regulated by hormones like estrogen and testosterone. Fats act as precursors for these chemicals and are, therefore, directly related to sexual drive.

Additionally, in women, fats form prostaglandins that maintain menstruation and ovulation. This is why low body fat percentage can lead to fertility issues.

Factors Affecting Body Fat Percentage

The following factors affect the body fat percentage:


Body composition and weight distribution have significant effects on body fat percentage, and changes in body shape and composition are important signs of aging.

As you grow old, your metabolic rate declines. After the age of 20, metabolism slows down by 2 to 3% every decade. Since fats are the slowest energy source, they take a lot of time to get metabolized, which naturally increases your body fat percentage.

After a person hits 40, the variations in metabolism, loss of muscle mass (and lean body mass), and rise in body fat become even more significant, which is why this age group is at a high risk of obesity and cardiovascular disease.


Gender is one of the most crucial variables of body fat distribution and body composition. Men have more muscle mass than women, as well as a more efficient metabolism for macronutrients (fats, proteins, and carbohydrates).

In contrast, women have a slightly slower metabolic rate and break down fewer fats than men, which allows them to accumulate as body fat (especially in hips and thighs).

This explains why in women, more than 32% of body fat is classified as obesity, whereas in men, a fat percentage above 25% is considered excessive.

Current Weight and Body Height

Your current weight and body height, body surface, and frame size are all critical determinants of body fat percentage.

Physical Activity

Physical activity determines your metabolic rate and total daily energy expenditure. If a person is active (exercises frequently or is involved in physical labor), they need high energy and thus have a high metabolic rate. This implies that more body fat is burned throughout the day.

On the other hand, a person who leads an inactive or sedentary lifestyle requires and burns fewer calories and thus has a high body fat percentage.

There are six levels of physical activity:

  • Sedentary: Little to no exercise
  • Light: Exercise 1 to 3 times a week
  • Moderate: Exercise 4 to 5 times a week
  • Active: Daily exercise or intense exercise 3 to 4 times a week
  • Very Intense: Daily intense exercise
  • Extra Active: Very intense exercise daily or a physical job

In the above classification:

  • Exercise – 15 to 30 minutes of increased heart rate
  • Intense exercise – 45 to 120 minutes of high heart rate
  • Very intense exercise – 2+ hours of increased heart rate

Fat Intake

The last thing on our list, yet the most defining factor of body fat percentage, is fat intake. This includes both the quantity and type of fats you consume in your diet.

Quantity Of Fat

When considering weight loss, most people fancy a low-calorie diet that reduces their fat intake. However, knowing the harmful effects of inadequate levels of body fat, we must be mindful of including at least the essential fat content in our diet.

Generally, 20% to 35% of fats are advised in meals, along with 10 to 35% proteins and 45 to 65% carbohydrates. Given that women and men are advised 2000 and 2500 daily calories, respectively, eating roughly 66 grams of fat in a day is ideal.

However, these are just general estimates, and to know your required fat intake more accurately, you would need to use a daily fat intake calculator.

Type Of Dietary Fat

The type of calories you consume is as important as the total number of calories. Sourcing your body fat from healthy diet (organic, natural sources), instead of processed and packaged products has a lower risk of unhealthy fat percentage and obesity.

Natural oils are the most abundant sources of fats (100% consist of fats)

  • Sunflower oil
  • Canola oil
  • Olive oil
  • Corn oil
  • Soy oil

Other than this, dairy products like milk, egg yolk, and butter, seafood like salmon and fish oil, and meat are also rich in fats.

  • 100 gm Nuts (pistachio) – 45 gm fats
  • 100 gm Meat – 3.5 gm fats
  • 100 gm Fish (salmon) – 12 gm fats
  • 100 gm Butter and margarine – 81 gm fat

These fats are categorized into two types; saturated and unsaturated fats:

  • Saturated Fats: These are harmful fats found in nuts, oils, seeds, poultry, red meat, and dairy. They raise LDL cholesterol in the body, which increases the risk of cardiovascular disorders and type 2 diabetes. Due to these effects, the use of saturated fats should be limited to 30 gm a day for men and 20 gm a day for women.
  • Unsaturated Fats: These are healthy fats found in avocados, nuts, natural oils, and pumpkin seeds. They improve blood cholesterol levels and inflammation and help stabilize heart rhythms. The recommended content of unsaturated fats in a daily diet is 50 to 65% of total fat intake (which is 20 to 35%).

Saturated fats not only increase bad cholesterol (LDL), but they also increase unhealthy body fat, which increases the risk of obesity, and related health complications.

Measuring Body Fat Percentage

Body mass index (BMI) and a US Navy Method are used by a body fat calculator.

US Navy Method

In the US Navy Method, separate formulas for body fat percentage have been devised based on gender:

Body Fat Percentage For Men

BFP = 86.010 × log10 (abdomen – neck) – 70.041 × log10 (height) + 36.76

Body Fat Percentage For Women

BFP = 163.205 × log10 (waist + hip – neck) – 97.684 × log10 (height) – 78.387

In the above equations, all the body circumference measurements will be in inches (as per the US customary system).

In the case of men, take the waist measurements at a horizontal level around the navel (belly button) and at the point of smallest width for women. For neck measurements, measure the circumference below the larynx, ensuring the neck is not flared outwards.

For hip circumference in women, consider the point of the largest horizontal measure.

Note that these equations generate body fat percentage. For fat mass and lean mass (fat-free mass), use the following equations:

Fat mass = body fat x weight

Lean body mass = body weight – fat mass

Body Mass Index BMI Method

Body mass index or BMI is another method used widely to calculate body fat percentage.

BMI is essentially the ratio of your weight (in kg) to your height (in m2).

The results of these ratios are classified into four categories according to the World Health Organization (WHO):

  • Underweight = < 18.5
  • Normal weight = 18.5 to 24.9
  • Overweight = 25.0 to 29.9
  • Obese = > 30

Note that in the case of children and teens, BMI percentile growth charts are used.

Anyways, once your weight-to-height ratio or body mass index is calculated, the following formulas are used to generate  body fat percentage:

Body Fat Percentage In Adult Males

BFP = (1.20 × BMI) + (0.23 × Age) – 16.2

Body fat Percentage In Adult Females

BFP = (1.20 × BMI) + (0.23 × Age) – 5.4

Body fat Percentage In Boys

BFP = (1.51 × BMI) – (0.70 × Age) – 2.2

Body Fat Percentage in Girls

BFP = (1.51 × BMI) – (0.70 × Age) + 1.4

It is essential to mention that a body fat calculator can only estimate body fat, and methods like bioelectric impedance analysis and hydrostatic weighing are used for more accurate calculation of a person’s body fat.

How To Reduce Body Fat Percentage?

Several health complications and risk of early mortality are associated with obesity (high fat mass).

Measure body fat percentage using the online calculator. If it is higher than 10 to 31%, work on reducing body fat with the following tips:

  • Maintain a healthy lifestyle (minimal alcohol, no smoking, etc.)
  • To build and maintain muscle mass, (and get rid of excess fat), plan and consistently follow a workout routine.
  • Make sure your weight loss diet at least has the required, healthy amount of fats to prevent energy deficit.
  • To stay full for longer hours, consider adding more fiber to your daily diet.

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