Body Fat Percentage: How to Calculate and Interpret It?
The body fat percentage, also known as the body fat index (BFI), refers to the proportion of fat in total body weight, expressed as a percentage. This same measurement is also referred to as body fat mass or, in English, “body fat.” This percentage is always interpreted according to gender and age, since women physiologically have more essential fat than men.
This guide presents reference tables for body fat percentages for women and men, the various methods for calculating body fat, and how to interpret the results.
On this page
What is body fat?
Body fat refers to all the fat (adipose tissue) present in the body and is measured in kilograms. When expressed as a percentage of total body weight, it is known as the body fat percentage. It serves as an energy reserve, plays a role in hormone production, and protects the organs.
Body fat percentage is also interpreted based on the type of fat and its distribution. It is important to distinguish between:
- Essential fat, necessary for the body to function
- Stored fat, which serves as an energy reserve and increases when energy intake exceeds energy expenditure.
- Subcutaneous fat, which is located under the skin
- Visceral fat, which surrounds the abdominal organs. Excess visceral fat is problematic because it promotes inflammation and increases the risk of diabetes.
Body Fat in Women: Reference Table
Body fat percentage is naturally higher in women than in men, as hormonal differences influence the amount and distribution of fat. The American Council on Exercise (ACE) chart—which is the most widely used for determining body fat percentage, regardless of the measurement method used—distinguishes the following categories:
| Category | Women |
|---|---|
| Essential fat | 10 to 13% |
| Athletes | 14 to 20% |
| Physical Fitness | 21 to 24% |
| Acceptable | 25 to 31% |
| Obesity | 32% or more |
ACE (American Council on Exercise) Guidelines.
Age must also be taken into account when interpreting the results. The study by Gallagher et al. provides reference ranges associated with the normal BMI range. For women, these ranges are as follows:
| Age Group | Women |
|---|---|
| Ages 20 to 39 | 21 to 32% |
| Ages 40 to 59 | 23 to 33% |
| Ages 60 to 79 | 24 to 35% |
Source: Gallagher et al., American Journal of Clinical Nutrition, 2000.
To convert this percentage to kilograms, simply multiply the weight by the body fat percentage divided by 100. For example, a 35-year-old woman weighing 65 kg with a body fat percentage of 22% has 14.3 kg of fat: 65 × 22 ÷ 100 = 14.3 kg. Her body fat percentage falls within the recommended range for women aged 20 to 39, which is 21% to 32%.
Body Fat in Men: Reference Table
Men generally have a lower body fat percentage than women, while their proportion of muscle mass is higher. Fat distribution also differs, as men tend to store fat in the abdominal area.
| Category | Men |
|---|---|
| Essential fat | 2 to 5% |
| Athletes | 6 to 13% |
| Physical Fitness | 14 to 17% |
| Acceptable | 18 to 24% |
| Obesity | 25% or more |
ACE (American Council on Exercise) Guidelines.
| Age Group | Men |
|---|---|
| Ages 20 to 39 | From 8% to less than 20% |
| Ages 40 to 59 | From 11% to less than 22% |
| Ages 60 to 79 | From 13% to less than 25% |
Source: Gallagher et al., American Journal of Clinical Nutrition, 2000.
To convert this percentage to kilograms, simply multiply the weight by the body fat percentage divided by 100. For example, a 35-year-old man weighing 80 kg with a body fat percentage of 18% has 14.4 kg of fat: 80 × 18 ÷ 100 = 14.4 kg. His body fat percentage falls within the recommended range for men aged 20 to 39, which is 8% to less than 20%.
How do you calculate your body fat percentage?
The Body Fat Percentage Calculator
This is an approximate estimate based on the ACE grid. It is not a substitute for a measurement taken with a professional device.
Résultat indicatif, positionné sur la grille ACE — ne remplace pas une mesure par un appareil professionnel. (Formule US Navy = équation standard, non fournie dans le texte source.)
There are two ways to calculate body fat:
- Use a statistical formula based on weight, height, age, and sex, such as the Deurenberg formula.
- Perform a body composition analysis using a bioimpedance scale or a DXA scan.
Formulas provide an estimate based on personal characteristics, while devices actually measure body tissue to assess its fat content.
Deurenberg's formula for calculating the Body Fat Index (BFI)
The Deurenberg formula is a calculation that estimates body fat percentage based on three pieces of information: BMI, age, and sex. This formula was developed using data collected from a population to predict a probable value for a given profile.
Age and gender are used to refine the estimate, since two people with the same BMI may have different body fat percentages.
The calculation is done as follows:
Body Fat Mass Index (BFM) = (1.2 × BMI) + (0.23 × age) − (10.8 × S) − 5.4
- BMI is calculated by dividing weight in kilograms by height in meters squared: weight ÷ (height × height).
- Age is expressed in years.
- S is 1 for a man and 0 for a woman.
For example, for a 30-year-old woman with a BMI of 22, we substitute 0 for S, and the calculation yields:
(1.2 × 22) + (0.23 × 30) − 5.4 = an IMG of approximately 27.9%.
Good to know: This estimate has its limitations because it is based on statistics and does not apply to very muscular individuals, people under 15, or pregnant women. For example, in athletes, it often overestimates the actual rate, since a high BMI can be due to muscle mass, which would result in an overestimated IMG. For pregnant women, hormonal changes and water retention make the formula inapplicable.
U.S. Navy Formula
The U.S. Navy formula estimates body fat percentage based on waist circumference and several body measurements, taken with a tape measure. Developed for the U.S. Navy, this method uses the statistical relationships between body measurements and body fat percentage.
The necessary measures differ by gender:
- For men: height, neck circumference, and waist circumference, measured at the navel.
- For women: height, neck circumference, waist circumference at the narrowest point, and hip circumference at the widest part of the buttocks.
These measurements are then incorporated into an equation to calculate an estimated body fat percentage.
The skin-fold caliper
The skinfold caliper, also known as an adipometer, measures the thickness of a fold formed by the skin and the fat located just beneath it. Specifically, the professional pinches a fold between their fingers, separating it from the muscle, and then places the caliper over it to measure its thickness in millimeters at various points on the body.
This measurement has its limitations because a poorly grasped fold or a caliper placed in the wrong spot can alter the result. Furthermore, the caliper measures the fat accessible beneath the skin, so it does not directly measure visceral fat, which is located around the organs.
The impedance scale
Bioimpedance analysis using a professional device is the most accurate gold-standard test for measuring body fat, lean body mass, and body water. It works by sending a very weak, imperceptible electrical current through the body. This current flows more easily through muscles—which contain a lot of water—than through fat. The scale measures how well the body conducts this current and then uses that information to estimate the amounts of fat and muscle.
The HowBody professional impedance scale uses eight electrodes and four frequencies to analyze five areas separately: each arm, each leg, and the torso. HowBody supplements this assessment with a 3D body scan, which records body measurements and evaluates posture.
DXA
DXA is an imaging test that assesses body composition using low doses of X-rays. It allows for the separate estimation of fat mass, lean body mass, and bone mineral content. This method requires specialized equipment and trained personnel, which makes it more logistically challenging to administer than a measurement using an impedance scale.
How can you lose body fat?
To reduce body fat percentage, you need a moderate calorie deficit achieved through a balanced diet, combined with strength training and regular physical activity. The goal is to gradually reduce fat stores while preserving muscle mass.
Adjust the power supply
Fat loss generally relies on a calorie deficit—that is, an energy intake that is slightly lower than the body’s energy expenditure. It’s also important to consume enough protein, as it helps preserve muscle mass during weight loss. For a healthy adult trying to lose weight, an intake of about 1.2 to 1.6 grams of protein per kilogram per day can help preserve lean body mass.
Engage in regular physical activity
Walking, biking, or swimming increases energy expenditure and improves physical fitness. The WHO recommends that adults engage in 150 to 300 minutes of moderate-intensity activity per week. To get started, 30 minutes of brisk walking five days a week will help you reach the 150-minute goal.
Do strength training
During weight loss, the body can lose both fat and muscle. Strength training helps limit this muscle loss and maintain strength. Studies support its use in combination with dietary changes among adults who are overweight or obese. Aim for at least two workouts per week that target the major muscle groups: legs, back, chest, shoulders, arms, and abs.
Monitoring your body composition monthly helps ensure that the weight loss is coming from body fat and allows you to adjust your diet or workout routine accordingly.
Body Fat in a HowBody Assessment
In a HowBody assessment, body fat is measured using multifrequency segmental bioimpedance analysis with 8 touch electrodes. The body composition report provides body fat mass in kilograms, body fat percentage, and a segmental analysis of fat in the arms, torso, and legs, with each value plotted within its reference range.
The visceral fat level rounds out this assessment, and the history section organizes successive test results to show changes from one evaluation to the next. This type of measurement is performed by qualified professionals at gyms, weight-loss centers, spas, and medical offices.
Frequently Asked Questions
What is the ideal body fat percentage?
The ideal body fat percentage varies by gender andage, but a range of 8 to 20 percent is generally recommended for men and 20 to 30 percent for women. This range changes with age.
What foods should you prioritize to reduce body fat?
Protein-rich foods, such as eggs, fish, poultry, and legumes, help preserve muscle mass while losing fat. Vegetables, fruits, and whole grains provide fiber, which promotes feelings of fullness. The key is to maintain a moderate calorie deficit by limiting highly processed foods and sugary drinks.
Which sport helps you lose the most body fat?
No exercise targets fat loss in a specific area; weight loss depends primarily on an overall calorie deficit. Endurance activities such as running, cycling, or swimming burn a lot of calories, while strength training preserves muscle mass and supports metabolism. Combining the two on a regular basis remains the most effective approach because it combines energy expenditure with the maintenance of muscle mass.
What is the difference between IMG and BMI?
BMI simply relates weight to height, without specifying what that weight consists of. The IMG estimates body fat percentage either using a statistical formula or through direct measurement. A muscular athlete may have both a high BMI and a low IMG, which illustrates the limitations of the former indicator.
How do you calculate your body fat in kilograms?
Simply multiply your weight by your body fat percentage. A 70-kg person with a 25% body fat percentage therefore has 17.5 kg of body fat. This value in kilograms makes it possible to track fat loss in concrete terms, regardless of fluctuations in water or muscle mass that affect total weight.
Accurately measure your body fat percentage
A HowBody assessment measures your body fat using multifrequency segmental bioimpedance analysis and a 3D body scan.