Male:
BF% = 86.010 × log₁₀(waist − neck) − 70.041 × log₁₀(height) + 36.76
Female:
BF% = 163.205 × log₁₀(waist + hip − neck) − 97.684 × log₁₀(height) − 78.387
Measurements in centimeters. The US Navy method is accurate to within 3-4% of DEXA scans.
Body fat percentage is the total mass of fat divided by total body mass, expressed as a percentage. Unlike weight alone, body fat percentage provides a more accurate picture of your body composition and overall health. Two people can weigh the same but have vastly different body fat percentages depending on their muscle mass, bone density, and fat distribution. Understanding your body fat percentage helps you set realistic fitness goals and track meaningful progress beyond the scale.
Fat serves essential functions in the body including energy storage, hormone production, organ protection, and temperature regulation. However, excessive body fat, particularly visceral fat stored around internal organs, is associated with increased risk of cardiovascular disease, type 2 diabetes, certain cancers, and metabolic syndrome. Conversely, having too little body fat can lead to hormonal imbalances, weakened immune function, and nutrient deficiencies. Maintaining an optimal body fat percentage is crucial for both health and athletic performance.
The US Navy body fat formula was developed by the United States Navy as a simple, reliable method for assessing body composition without expensive equipment. This method uses circumference measurements at specific body sites along with height to estimate body fat percentage. For men, measurements are taken at the neck and waist; for women, an additional hip measurement is required. The formula has been validated against hydrostatic weighing and DEXA scans, showing accuracy within 3-4% for most individuals.
To get accurate measurements, use a flexible tape measure and take readings on bare skin. For the neck, measure just below the larynx (Adam's apple) at the narrowest point. For the waist, men should measure at the navel level, while women should measure at the narrowest point. For hips (women only), measure at the widest point of the buttocks. Take each measurement twice and use the average. Consistency in measurement technique is more important than absolute precision for tracking changes over time.
Body fat categories differ between men and women due to physiological differences. Women naturally carry more essential fat for reproductive functions and hormone production. Essential fat is the minimum amount required for normal physiological function—approximately 2-5% for men and 10-13% for women. Going below these levels can cause serious health problems including hormonal disruption, organ damage, and compromised immune function.
Athletes (Men: 6-13% | Women: 14-20%)
This range is typical for competitive athletes and those engaged in intensive training. At this level, muscle definition is visible and physical performance is optimized. Maintaining this range long-term requires dedicated training and nutrition, and may not be sustainable or healthy for everyone.
Fitness (Men: 14-17% | Women: 21-24%)
The fitness category represents a healthy, athletic body composition achievable through regular exercise and balanced nutrition. Most people who work out consistently fall into this range. Muscle definition is apparent, and this level is associated with excellent health markers.
Average (Men: 18-24% | Women: 25-31%)
This range is considered acceptable and represents the average body fat percentage for moderately active individuals. While not optimal for athletic performance, this range is generally healthy and sustainable for most people with moderate exercise habits.
Obese (Men: 25%+ | Women: 32%+)
Body fat percentages in this range are associated with increased health risks including cardiovascular disease, insulin resistance, joint problems, and certain cancers. If you fall into this category, working with healthcare professionals to develop a sustainable fat loss plan is recommended.
Reducing body fat requires a sustainable approach combining nutrition, exercise, and lifestyle modifications. Creating a moderate caloric deficit of 300-500 calories per day promotes fat loss while preserving muscle mass. Focus on whole foods including lean proteins, vegetables, fruits, whole grains, and healthy fats. Protein intake of 0.7-1 gram per pound of body weight supports muscle retention during weight loss. Avoid extreme diets that promise rapid results, as they often lead to muscle loss and metabolic adaptation.
Resistance training is crucial for maintaining and building muscle during fat loss. Aim for 2-4 strength training sessions per week, focusing on compound movements like squats, deadlifts, presses, and rows. Add 2-3 sessions of cardiovascular exercise, mixing steady-state cardio with high-intensity interval training (HIIT) for optimal fat burning. Sleep 7-9 hours per night to support hormone balance and recovery. Manage stress through meditation, deep breathing, or other relaxation techniques, as chronic stress elevates cortisol which promotes fat storage, particularly around the midsection.
While body fat calculators provide useful estimates, they have limitations. The US Navy method assumes typical fat distribution patterns and may be less accurate for individuals with unusual body proportions, very lean athletes, or those with significant muscle mass. The BMI-based method is even less precise as it doesn't account for body composition differences. For the most accurate body fat measurement, consider professional methods like DEXA scans, hydrostatic weighing, or air displacement plethysmography (Bod Pod).
Use this calculator as a tracking tool rather than an absolute measure. What matters most is the trend over time rather than any single measurement. Take measurements consistently—same time of day, same conditions—and track changes over weeks and months. Remember that body fat percentage is just one metric of health. Focus on how you feel, your energy levels, physical performance, and other health markers alongside body composition goals. If you have concerns about your body fat percentage or health, consult with a healthcare professional or registered dietitian.