Body fat percentage is the proportion of your body weight that comes from fat tissue versus lean tissue (muscle, bone, organs, water). Unlike BMI, which only considers height and weight, body fat percentage gives you a more accurate picture of your body composition and health.
The U.S. Navy body fat calculator uses simple circumference measurements (neck, waist, and hip for women) to estimate body fat percentage. It was developed as a practical field method that doesn't require expensive equipment or underwater weighing. While not as accurate as DEXA scans, it provides a reliable estimate that's consistent and easy to track over time.
Neck: Measure around the smallest part, just below the Adam's apple. Keep tape horizontal.
Waist: For women, measure at the narrowest point (usually at navel level). For men, measure at the widest part of the abdomen.
Hip (women only): Measure around the widest part of the buttocks, keeping tape parallel to the floor.
Tips: Measure in the morning before eating, use a flexible tape measure, keep the tape snug but not tight, and measure the same spots each time for consistency.
Your body fat percentage is more meaningful than scale weight alone. Two people can weigh the same but have vastly different body compositions. Lower body fat with higher lean mass means a healthier, more metabolically active body.
The "ideal" body fat varies by age, gender, and goals. Women naturally carry more essential fat (10-13%) than men (2-5%). As we age, some increase in body fat is normal, but maintaining muscle mass through strength training and adequate protein intake helps preserve metabolic health.
The Navy method is an estimate, not a precise measurement. It works well for most people but may be less accurate for very lean individuals, bodybuilders, or those with unusual body proportions. Factors like hydration, time of day, and measurement technique can affect results. Use it as one tool among many to track progress over time.