The composition of the human body
More than 98% of the human body is composed of six elements: oxygen, carbon, hydrogen, nitrogen, calcium, and phosphorus. Potassium, sulfur, sodium, chlorine, and magnesium are responsible for almost another 1%. These are the 11 most important, so called non-trace, elements.
Regarding the molecules, the most common molecule in the human body is of course water, which takes about 65% of mass, followed by proteins and lipids. Other molecules which have a decent percent of mass are hydroxyapatite, carbohydrates and nucleic acids.
What is body fat?
It is actually adipose tissue; its main function is to store energy in the form of lipids, but it cushions and insulates your body, too. Your body stores two types of fat: essential and storage body fat. The former is necessary to support life and reproductive functions. Essential body fat is substantially higher for women because of childbearing and hormonal functions. Storage body fat is the mass of additional accumulated fat. It does not mean that this type of body fat is unnecessary, though — part of it protects your abdomen and internal organs.
How to calculate body fat?
You can estimate your body composition with our body fat percentage calculator. Remember that no calculator, however complicated, can replace a visit to a doctor's office. You should treat this result as a rough estimate; it can only tell you if your body fat percentage is drastically too high, but there's no reason to panic if the result differs slightly from the recommended value.
To calculate the body fat percentage, you need to enter the following data:
- Your sex.
- Choose the calculation method:
- American Diabetes Association — most commonly used;
- U.S. Navy — most precise but requires additional neck, waist, and hip circumference measurements;
- BMI — least precise but useful for comparison.
- Height: stand straight and measure the distance from the floor to the top of your head. Remember — no shoes!
- Weight: simply weigh yourself. You will get the most accurate result weighing yourself in the morning, before breakfast, and without clothes on.
If you choose the U.S. Navy method, you also need to measure:
- Waist circumference: For men, measure horizontally at the level of the navel. For women, measure at the narrowest part of the waist.
- Neck circumference: Place the tape just below the larynx (Adam's apple), angled slightly downward to the front.
- Hip circumference (women only): Measure around the widest part of the hips.
The American Diabetes Association formula for adults is:
Body fat % = −44.988 + (0.503 × age) + (10.689 × sex) + (3.172 × BMI) − (0.026 × BMI²) + (0.181 × BMI × sex) − (0.02 × BMI × age) − (0.005 × BMI² × sex) + (0.00021 × BMI² × age)
Where: Sex value: male = 0 and female = 1; BMI = weight / height² [kg/m²]. This equation was validated on 6,510 people with an estimated error of 4.66%.
Is my body fat percentage normal?
Once you calculate your body fat percentage, compare it with the recommended values from the American Council on Exercise (ACE):
- Essential fat: 10%–13% (women), 2%–5% (men)
- Athletes: 14%–20% (women), 6%–13% (men)
- Fitness: 21%–24% (women), 14%–17% (men)
- Average: 25%–31% (women), 18%–24% (men)
- Obese: 32%+ (women), 25%+ (men)
If your body fat percentage is lower than 31% for women and 24% for men, you are in the average range and have nothing to worry about. Higher levels of body fat may be dangerous for your health.
Why should I control my body fat?
Excess body fat is associated with numerous health risks, including cardiovascular disease, type 2 diabetes, high blood pressure, sleep apnea, and certain cancers. On the other hand, too little body fat can disrupt hormonal balance, impair immune function, and lead to nutritional deficiencies. Maintaining body fat within a healthy range supports optimal organ function, energy levels, and overall well-being.
Alternative methods of measuring body fat
- DEXA scan (Dual-Energy X-ray Absorptiometry) — the gold standard, highly accurate but requires medical equipment.
- Hydrostatic weighing — underwater weighing, very accurate but impractical for most people.
- Skinfold calipers — measures fat thickness at specific body sites, reasonably accurate when done correctly.
- Bioelectrical impedance analysis (BIA) — uses electrical current through the body; convenient but accuracy varies.
- Air displacement plethysmography (Bod Pod) — measures body volume to estimate fat percentage.
How to reduce body fat?
To reduce body fat, focus on a combination of:
- Caloric deficit: Consuming fewer calories than you burn forces your body to use stored fat for energy.
- Strength training: Building muscle increases your resting metabolic rate, helping you burn more fat at rest.
- Cardiovascular exercise: Aerobic activities like running, cycling, or swimming help burn calories efficiently.
- Protein intake: A high-protein diet helps preserve muscle mass while losing fat.
- Sleep and stress management: Poor sleep and high cortisol levels promote fat storage, especially around the abdomen.
Is fat so bad?
Not at all — fat is essential! Essential body fat is critical for brain function, hormone production, and protecting vital organs. Problems arise when fat accumulates in excess, particularly visceral fat (around the organs). The key is balance: enough fat to support bodily functions, but not so much that it impairs health.
FAQs
How accurate is the body fat calculator?
The ADA formula has an estimated error of ±4.66%. The U.S. Navy method is generally more accurate when circumference measurements are taken correctly. No formula perfectly accounts for individual body composition variability.
Can I have a high BMI but low body fat?
Yes — very muscular individuals may have a high BMI (since muscle is denser than fat) while having a low body fat percentage. This is why BMI alone is not a complete picture of health.
How often should I measure my body fat?
Measuring once a month is typically sufficient. More frequent measurements may show noise rather than meaningful trends.