Estimate your body fat percentage using the U.S. Navy method as the primary result, plus a BMI-based estimate for comparison.
The Body Fat Calculator estimates your body fat percentage using two independent methods: the U.S. Navy circumference method as the primary result, and a BMI-based estimate as a secondary reference. Comparing both gives a useful range to work with, even though neither is as precise as clinical methods like a DEXA scan.
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 measurements in inches (or centimeters for metric mode). This formula was developed by Hodgdon and Beckett at the Naval Health Research Center and is used by the U.S. military to assess fitness eligibility.
The secondary BMI-based estimate uses the Deurenberg formula:
Body Fat % = (1.20 × BMI) + (0.23 × age) − (10.8 × sex) − 5.4 (sex: 1 = male, 0 = female)
This estimate is less precise but requires only height and weight.
Measure in the morning before eating or exercising, wearing minimal clothing. Repeat each measurement twice and average the results for best accuracy.
BMI uses only weight and height, which means it can't distinguish fat from muscle. Body fat percentage is a more accurate indicator of body composition — a muscular athlete and a sedentary person can have identical BMIs but vastly different body fat levels. When possible, use both metrics together for a fuller picture. See the BMI Calculator for comparison, and use the BMR Calculator to estimate your daily calorie needs based on your lean body composition.
This calculator uses two methods: the U.S. Navy circumference method as the primary result, and a BMI-based estimate as secondary. The Navy method uses your height, neck, waist, and (for women) hip circumference to estimate body fat using a validated logarithmic formula developed by Hodgdon and Beckett.
The U.S. Navy method is generally more accurate than the BMI-based estimate because it uses direct body measurements rather than just weight and height. However, both are estimates. True body fat percentage is most accurately measured by DEXA scan, hydrostatic weighing, or air displacement plethysmography (Bod Pod) — clinical methods that cost more and require equipment.
General guidelines by category — Men: Essential fat: 2–5%; Athlete: 6–13%; Fitness: 14–17%; Average: 18–24%; Obese: 25%+. Women: Essential fat: 10–13%; Athlete: 14–20%; Fitness: 21–24%; Average: 25–31%; Obese: 32%+. These ranges vary slightly by source and individual health context.
Men need: height, weight, neck circumference (measured at the narrowest point below the larynx), and waist circumference (measured at the navel). Women add: hip circumference (measured at the widest point). Measure snugly but without compressing the skin. Consistent technique matters — slight variations in tape placement can shift results by 1–3%.
Essential fat is the minimum amount your body needs to function — protecting organs, regulating hormones, and enabling proper nerve function. For men, this is approximately 2–5%. For women, it's approximately 10–13% due to sex-specific fat in the breasts, uterus, and other reproductive areas. Going below essential fat levels is dangerous and associated with organ failure.
No. While excess body fat increases health risk, very low body fat can also be harmful. Extremely lean athletes often experience hormonal disruption, reduced immune function, and increased injury risk. For most non-athletes, a 'fitness' range (14–17% for men, 21–24% for women) balances health and performance well. Competitive bodybuilding levels (sub-6% for men) are not sustainable long-term.
The most effective approach combines a moderate calorie deficit (10–20% below TDEE) with resistance training to preserve muscle mass. High protein intake (1.6–2.2 g/kg) is critical — it preserves lean mass while losing fat. Cardio accelerates the deficit. Avoid crash dieting, which causes muscle loss alongside fat loss, raising body fat percentage over the long term.
The U.S. Navy method typically estimates body fat within 3–5 percentage points of DEXA results for most people. Accuracy is best for people of average build with consistent measurement technique. It tends to be less accurate for very lean individuals (where it may overestimate) and very obese individuals. Use it as a useful tracking tool — consistent measurements over time are more valuable than any single absolute number.