What Is Body Fat Percentage?

Body fat percentage is the proportion of your total body weight that is made up of fat tissue. Unlike BMI, which only accounts for weight relative to height, body fat percentage distinguishes between fat mass and lean mass (muscle, bone, water, and organs). This makes it a far more meaningful indicator of fitness level and overall health.

Two people can share the same weight and height yet have dramatically different body compositions. A trained athlete at 80 kg may carry 12% body fat, while a sedentary individual at 80 kg could be at 28%. Their BMI would be identical, but their health profiles would be vastly different. Knowing your body fat percentage helps you set realistic goals, track progress from a resistance training program, and identify health risks that BMI alone would miss.

Body Fat Percentage Categories

The American Council on Exercise (ACE) provides the following general classification ranges for body fat percentage:

Category	Men	Women
Essential Fat	2 – 5%	10 – 13%
Athletes	6 – 13%	14 – 20%
Fitness	14 – 17%	21 – 24%
Average	18 – 24%	25 – 31%
Obese	25%+	32%+

Women naturally carry more essential body fat than men due to reproductive functions and hormonal differences. Essential fat is the minimum amount of fat necessary for normal physiological function. Dropping below essential fat levels is dangerous and can lead to hormonal disruption, loss of menstrual cycle in women, weakened immune function, and organ damage.

The US Navy Method

The US Navy body fat formula was developed by Hodgdon and Beckett at the Naval Health Research Center in 1984. It uses circumference measurements of the waist, neck, and hips (for women) along with height to estimate body fat percentage. The method was originally designed for military fitness assessments and remains widely used because it requires only a flexible tape measure.

The formulas use logarithmic calculations:

Men: BF% = 86.010 x log10(waist - neck) - 70.041 x log10(height) + 36.76
Women: BF% = 163.205 x log10(waist + hip - neck) - 97.684 x log10(height) - 78.387

Studies have shown the Navy method to be accurate within 3-4% of results obtained by hydrostatic weighing, which is considered a gold-standard measurement technique. The key to accuracy is consistent, precise tape placement. Measure your waist at the narrowest point (typically at the navel for men, or just above the hip bones), your neck at the narrowest point below the larynx, and your hips at the widest point of the buttocks.

BMI-Based Estimation

The BMI-based method uses a formula derived by Deurenberg et al. (1991) that estimates body fat from BMI, age, and sex. While less accurate than the Navy method for individuals, it provides a reasonable population-level estimate. The formula is: BF% = (1.20 x BMI) + (0.23 x age) - (10.8 x sex) - 5.4, where sex is 1 for males and 0 for females. This method is useful when circumference measurements are not available, but it shares many of BMI's limitations regarding muscle mass.

Other Measurement Techniques

Beyond the Navy method and BMI estimation, several other techniques exist for measuring body fat, each with different trade-offs between accuracy, cost, and accessibility:

DEXA Scan: Dual-energy X-ray Absorptiometry is considered the clinical gold standard. It provides a full body composition breakdown including regional fat distribution and bone density. Accuracy is within 1-2%, but scans cost $50-150 per session and require specialized equipment.
Hydrostatic Weighing: This underwater weighing method was historically the gold standard. It calculates body density by comparing your weight on land to your weight submerged in water. It is accurate within 1-2% but requires specialized facilities and can be uncomfortable.
Skinfold Calipers: A trained technician measures skin folds at 3-7 body sites and applies standardized equations. When performed correctly, accuracy is within 3-4%. Results vary significantly with the skill of the person taking the measurements.
Bioelectrical Impedance (BIA): BIA scales and handheld devices send a small electrical current through your body and estimate fat based on resistance. While convenient and inexpensive, accuracy varies widely (error of 3-8%) and is heavily influenced by hydration level, recent meals, and exercise.
Bod Pod: Air displacement plethysmography measures body volume using air pressure changes inside a sealed chamber. Accuracy is similar to hydrostatic weighing (within 1-2%) and is more comfortable, but access is limited to research facilities and some gyms.

Health Implications of Body Fat

Excess body fat, particularly visceral fat stored around the internal organs in the abdominal region, is strongly linked to metabolic syndrome, type 2 diabetes, cardiovascular disease, and certain cancers. Visceral fat is metabolically active tissue that releases inflammatory compounds and disrupts hormone regulation. This is why waist circumference is such a valuable health indicator independent of overall body fat percentage.

On the other end of the spectrum, excessively low body fat is also harmful. Athletes who maintain very low body fat levels for extended periods may experience Relative Energy Deficiency in Sport (RED-S), which can cause hormonal imbalances, reduced bone density, impaired immune function, and decreased athletic performance. A sustainable body fat percentage for active individuals is typically in the fitness range: 14-17% for men and 21-24% for women.

Reducing Body Fat Safely

Healthy fat loss requires a moderate calorie deficit combined with adequate protein intake and resistance training. Aim to lose no more than 0.5-1% of body weight per week to preserve lean mass. Protein intake of 1.6-2.2 grams per kilogram of body weight per day helps maintain muscle during a deficit. Resistance training provides the mechanical stimulus your muscles need to remain intact even as you lose weight.

Crash diets and extreme calorie restrictions may cause rapid weight loss, but much of that loss will be muscle and water rather than fat. This leads to a higher body fat percentage at a lower body weight, sometimes referred to as "skinny fat." Patience and consistency are essential for meaningful and lasting body composition improvements.

Next step: Know your body fat percentage? Use the TDEE Calculator to find your daily calorie needs, then create a plan with the Macro Calculator for optimal body composition.

Frequently Asked Questions

The US Navy method is accurate within 3-4% of hydrostatic (underwater) weighing for most individuals. Its accuracy depends on precise, consistent tape placement. Measure your waist at the narrowest point, neck at the narrowest point below the larynx, and hips at the widest point. For the most reliable results, take each measurement three times and use the average.

For men, the fitness range is 14-17% and the acceptable average range is 18-24%. For women, the fitness range is 21-24% and the acceptable average range is 25-31%. Athletes often maintain lower levels (6-13% for men, 14-20% for women), but these require dedicated training and nutrition programs and may not be sustainable long-term.

Women carry more essential fat (10-13% vs. 2-5% for men) due to biological requirements for reproductive function, hormonal regulation, and breast tissue. This is a normal and healthy difference. Comparing body fat percentages across sexes using the same scale is not meaningful, which is why separate ranges exist for men and women.

Body fat percentage is a more accurate indicator of health and fitness because it distinguishes between fat mass and lean mass. BMI treats all weight the same, so a muscular person may be classified as overweight or obese by BMI despite having low body fat. However, BMI remains useful as a quick, easy screening tool when body composition data is not available.

For men, measure at the navel level while standing relaxed. For women, measure at the narrowest part of the torso, typically about one inch above the navel. Do not suck in your stomach. Use a flexible tape measure pulled snug against the skin but not compressing it. Measure directly against the skin, not over clothing.

Yes, with the right approach. Maintain a moderate calorie deficit (300-500 calories below your TDEE), eat sufficient protein (1.6-2.2g per kg of body weight per day), and follow a progressive resistance training program. Avoid crash diets and excessive cardio, which accelerate muscle loss. Aim for a weight loss rate of 0.5-1% of body weight per week.

Measure every 2-4 weeks under consistent conditions: same time of day, same hydration status, same person taking the measurements. Body fat changes slowly, so measuring more frequently tends to create noise rather than useful data. Track the trend over months rather than focusing on any single measurement.

Subcutaneous fat is stored directly under the skin and is what you can pinch. Visceral fat is stored around internal organs in the abdominal cavity. Visceral fat is more metabolically dangerous because it releases inflammatory compounds and hormones that increase the risk of heart disease, diabetes, and metabolic syndrome. Waist circumference is a practical proxy for visceral fat levels.

Body Fat Calculator