Body Fat Percentage Calculator (Navy Method)

Follow these steps to estimate your body fat percentage:

1. Select your gender. The Navy formula uses different equations for men and women because fat distribution patterns differ between the sexes.
2. Enter your age and weight in pounds. Age provides context for your body fat category, and weight is used to calculate fat mass and lean mass.
3. Enter your height in total inches. Convert feet and inches by multiplying feet by 12 and adding the remaining inches (for example, 5 feet 10 inches equals 70 inches).
4. Measure your neck circumference. Wrap a flexible, non-elastic measuring tape around the narrowest part of your neck, just below the larynx (Adam's apple). Keep the tape level and snug but not compressing the skin.
5. Measure your waist circumference. For men, measure at the navel. For women, measure at the narrowest point of the natural waistline. Stand relaxed and do not suck in your stomach.
6. Measure your hip circumference (women only). Wrap the tape around the widest point of the buttocks and hips, keeping it level.

Tips for consistent and accurate measurements: Always measure at the same time of day, ideally in the morning before eating. Take each measurement two to three times and use the average. Use a mirror or ask someone to help ensure the tape is level. Record your measurements so you can track changes over time. Avoid measuring immediately after exercise, as temporary swelling can skew results. Consistent technique matters more than any single reading.

Body fat percentage is the proportion of your total body weight that is composed of fat tissue. It is one of the most meaningful indicators of physical health and fitness, far more informative than body weight alone or even Body Mass Index (BMI). While BMI uses only height and weight, body fat percentage distinguishes between fat mass and lean mass, which includes muscle, bone, water, and organs. Two individuals with identical BMIs can have dramatically different body compositions; a muscular athlete may register as "overweight" on BMI while actually carrying very low body fat.

Body fat is categorized into two types: essential fat and storage fat. Essential fat is required for normal physiological function, including hormone regulation, insulation of organs, and vitamin absorption. Men need a minimum of roughly 2 to 5 percent essential fat, while women require 10 to 13 percent due to additional fat needed for reproductive health. Storage fat accumulates beneath the skin (subcutaneous fat) and around organs (visceral fat) as an energy reserve. Healthy body fat ranges differ by sex and age. For men, the fitness range is generally 14 to 17 percent, and the average healthy range extends up to 24 percent. For women, fitness falls between 21 and 24 percent, with the healthy average extending to about 31 percent.

This calculator uses the U.S. Navy method, a circumference-based formula developed by Hodgdon and Beckett at the Naval Health Research Center. It estimates body fat from simple tape measurements of the neck, waist, and hips (for women), along with height. The Navy method is valued for its accessibility since it requires no special equipment, and its accuracy is typically within 1 to 3 percent of hydrostatic (underwater) weighing results. Monitoring body fat percentage over time is more useful than tracking weight alone because it reveals whether you are losing fat, gaining muscle, or both. Excessively high body fat increases the risk of cardiovascular disease, type 2 diabetes, and metabolic syndrome, while excessively low body fat can disrupt hormones, impair immune function, and reduce bone density.

The U.S. Navy body fat formulas use circumference measurements and height with base-10 logarithms:

• Men: Body Fat % = 495 ÷ (1.0324 − 0.19077 × log₁₀(waist − neck) + 0.15456 × log₁₀(height)) − 450
• Women: Body Fat % = 495 ÷ (1.29579 − 0.35004 × log₁₀(waist + hip − neck) + 0.22100 × log₁₀(height)) − 450

All circumference and height measurements must be in inches. The formula relies on the principle that body fat distribution correlates with the ratio of certain circumference measurements to height. The logarithmic transformation accounts for the nonlinear relationship between circumferences and body density.

After obtaining body fat percentage, the remaining values are derived as follows:

• Fat Mass = (Body Fat % ÷ 100) × Total Body Weight
• Lean Mass = Total Body Weight − Fat Mass

Variable definitions:

Example 1 — Fit Male: A 175 lb male, 71 inches tall, with a 15.5-inch neck and 32-inch waist. Circumference value = 32 − 15.5 = 16.5. Body Fat % = 495 ÷ (1.0324 − 0.19077 × log₁₀(16.5) + 0.15456 × log₁₀(71)) − 450 = 495 ÷ (1.0324 − 0.2321 + 0.2862) − 450 = 495 ÷ 1.0865 − 450 ≈ 5.6%. Fat mass = 0.056 × 175 = 9.8 lbs. Lean mass = 165.2 lbs. This individual falls into the Athletes category for men, which ranges from 6 to 13 percent. At 5.6% he is approaching essential fat levels and would need to ensure he is not underfueling for health.

Example 2 — Average Female: A 155 lb female, 66 inches tall, with a 13-inch neck, 31-inch waist, and 40-inch hip. Circumference value = 31 + 40 − 13 = 58. Body Fat % = 495 ÷ (1.29579 − 0.35004 × log₁₀(58) + 0.22100 × log₁₀(66)) − 450 = 495 ÷ (1.29579 − 0.6174 + 0.4019) − 450 = 495 ÷ 1.0803 − 450 ≈ 8.1%. Fat mass = 0.081 × 155 = 12.6 lbs. Lean mass = 142.4 lbs. At roughly 28 percent, she falls in the Average category for women (25 to 31 percent), which is considered a healthy range for general health. To move into the Fitness category, she would need to reduce body fat below 25 percent through a modest calorie deficit and resistance training.

Example 3 — Athlete Comparison: Consider two males who both weigh 185 lbs and stand 70 inches tall. Athlete A has a 16-inch neck and 31-inch waist, yielding a body fat percentage of approximately 13.3 percent (Athletes category). Athlete B has a 14.5-inch neck and 37-inch waist, yielding approximately 23.7 percent (Average category). Despite identical weight and height, Athlete A carries roughly 24.6 lbs of fat and 160.4 lbs of lean mass, while Athlete B carries approximately 43.8 lbs of fat and only 141.2 lbs of lean mass. This comparison illustrates exactly why body fat percentage is a far more revealing metric than weight or BMI alone.